WorldWideScience

Sample records for modeling spatial variation

  1. Constraining spatial variations of the fine-structure constant in symmetron models

    Science.gov (United States)

    Pinho, A. M. M.; Martinelli, M.; Martins, C. J. A. P.

    2017-06-01

    We introduce a methodology to test models with spatial variations of the fine-structure constant α, based on the calculation of the angular power spectrum of these measurements. This methodology enables comparisons of observations and theoretical models through their predictions on the statistics of the α variation. Here we apply it to the case of symmetron models. We find no indications of deviations from the standard behavior, with current data providing an upper limit to the strength of the symmetron coupling to gravity (log ⁡β2 constrain the model when also the symmetry breaking scale factor aSSB is free to vary.

  2. Investigation of Spatial Variation of Sea States Offshore of Humboldt Bay CA Using a Hindcast Model.

    Energy Technology Data Exchange (ETDEWEB)

    Dallman, Ann Renee; Neary, Vincent Sinclair

    2014-10-01

    Spatial variability of sea states is an important consideration when performing wave resource assessments and wave resource characterization studies for wave energy converter (WEC) test sites and commercial WEC deployments. This report examines the spatial variation of sea states offshore of Humboldt Bay, CA, using the wave model SWAN . The effect of depth and shoaling on bulk wave parameters is well resolved using the model SWAN with a 200 m grid. At this site, the degree of spatial variation of these bulk wave parameters, with shoaling generally perpendicular to the depth contours, is found to depend on the season. The variation in wave height , for example, was higher in the summer due to the wind and wave sheltering from the protruding land on the coastline north of the model domain. Ho wever, the spatial variation within an area of a potential Tier 1 WEC test site at 45 m depth and 1 square nautical mile is almost negligible; at most about 0.1 m in both winter and summer. The six wave characterization parameters recommended by the IEC 6 2600 - 101 TS were compared at several points along a line perpendicular to shore from the WEC test site . As expected, these parameters varied based on depth , but showed very similar seasonal trends.

  3. Quantifying geographic variation in the climatic drivers of midcontinent wetlands with a spatially varying coefficient model.

    Science.gov (United States)

    Roy, Christian

    2015-01-01

    The wetlands in the Prairie Pothole Region and in the Great Plains are notorious for their sensitivity to weather variability. These wetlands have been the focus of considerable attention because of their ecological importance and because of the expected impact of climate change. Few models in the literature, however, take into account spatial variation in the importance of wetland drivers. This is surprising given the importance spatial heterogeneity in geomorphology and climatic conditions have in the region. In this paper, I use spatially-varying coefficients to assess the variation in ecological drivers in a number of ponds observed over a 50-year period (1961-2012). I included the number of ponds observed the year before on a log scale, the log of total precipitation, and mean maximum temperature during the four previous seasons as explanatory variables. I also included a temporal component to capture change in the number of ponds due to anthropogenic disturbance. Overall, fall and spring precipitation were most important in pond abundance in the west, whereas winter and summer precipitation were the most important drivers in the east. The ponds in the east of the survey area were also more dependent on pond abundance during the previous year than those in the west. Spring temperature during the previous season influenced pond abundance; while the temperature during the other seasons had a limited effect. The ponds in the southwestern part of the survey area have been increasing independently of climatic conditions, whereas the ponds in the northeast have been steadily declining. My results underline the importance of accounting the spatial heterogeneity in environmental drivers, when working at large spatial scales. In light of my results, I also argue that assessing the impacts of climate change on wetland abundance in the spring, without more accurate climatic forecasting, will be difficult.

  4. Spatial variations and development of land use regression models of oxidative potential in ten European study areas

    Science.gov (United States)

    Jedynska, Aleksandra; Hoek, Gerard; Wang, Meng; Yang, Aileen; Eeftens, Marloes; Cyrys, Josef; Keuken, Menno; Ampe, Christophe; Beelen, Rob; Cesaroni, Giulia; Forastiere, Francesco; Cirach, Marta; de Hoogh, Kees; De Nazelle, Audrey; Nystad, Wenche; Akhlaghi, Helgah Makarem; Declercq, Christophe; Stempfelet, Morgane; Eriksen, Kirsten T.; Dimakopoulou, Konstantina; Lanki, Timo; Meliefste, Kees; Nieuwenhuijsen, Mark; Yli-Tuomi, Tarja; Raaschou-Nielsen, Ole; Janssen, Nicole A. H.; Brunekreef, Bert; Kooter, Ingeborg M.

    2017-02-01

    Oxidative potential (OP) has been suggested as a health-relevant measure of air pollution. Little information is available about OP spatial variation and the possibility to model its spatial variability. Our aim was to measure the spatial variation of OP within and between 10 European study areas. The second aim was to develop land use regression (LUR) models to explain the measured spatial variation. OP was determined with the dithiothreitol (DTT) assay in ten European study areas. DTT of PM2.5 was measured at 16-40 sites per study area, divided over street, urban and regional background sites. Three two-week samples were taken per site in a one-year period in three different seasons. We developed study-area specific LUR models and a LUR model for all study areas combined to explain the spatial variation of OP. Significant contrasts between study areas in OP were found. OP DTT levels were highest in southern Europe. DTT levels at street sites were on average 1.10 times higher than at urban background locations. In 5 of the 10 study areas LUR models could be developed with a median R2 of 33%. A combined study area model explained 30% of the measured spatial variability. Overall, LUR models did not explain spatial variation well, possibly due to low levels of OP DTT and a lack of specific predictor variables.

  5. Bayesian spatial semi-parametric modeling of HIV variation in Kenya.

    Directory of Open Access Journals (Sweden)

    Oscar Ngesa

    Full Text Available Spatial statistics has seen rapid application in many fields, especially epidemiology and public health. Many studies, nonetheless, make limited use of the geographical location information and also usually assume that the covariates, which are related to the response variable, have linear effects. We develop a Bayesian semi-parametric regression model for HIV prevalence data. Model estimation and inference is based on fully Bayesian approach via Markov Chain Monte Carlo (McMC. The model is applied to HIV prevalence data among men in Kenya, derived from the Kenya AIDS indicator survey, with n = 3,662. Past studies have concluded that HIV infection has a nonlinear association with age. In this study a smooth function based on penalized regression splines is used to estimate this nonlinear effect. Other covariates were assumed to have a linear effect. Spatial references to the counties were modeled as both structured and unstructured spatial effects. We observe that circumcision reduces the risk of HIV infection. The results also indicate that men in the urban areas were more likely to be infected by HIV as compared to their rural counterpart. Men with higher education had the lowest risk of HIV infection. A nonlinear relationship between HIV infection and age was established. Risk of HIV infection increases with age up to the age of 40 then declines with increase in age. Men who had STI in the last 12 months were more likely to be infected with HIV. Also men who had ever used a condom were found to have higher likelihood to be infected by HIV. A significant spatial variation of HIV infection in Kenya was also established. The study shows the practicality and flexibility of Bayesian semi-parametric regression model in analyzing epidemiological data.

  6. Spatial Variation of Soil Type and Soil Moisture in the Regional Atmospheric Modeling System

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, R.

    2001-06-27

    Soil characteristics (texture and moisture) are typically assumed to be initially constant when performing simulations with the Regional Atmospheric Modeling System (RAMS). Soil texture is spatially homogeneous and time-independent, while soil moisture is often spatially homogeneous initially, but time-dependent. This report discusses the conversion of a global data set of Food and Agriculture Organization (FAO) soil types to RAMS soil texture and the subsequent modifications required in RAMS to ingest this information. Spatial variations in initial soil moisture obtained from the National Center for Environmental Predictions (NCEP) large-scale models are also introduced. Comparisons involving simulations over the southeastern United States for two different time periods, one during warmer, more humid summer conditions, and one during cooler, dryer winter conditions, reveals differences in surface conditions related to increases or decreases in near-surface atmospheric moisture con tent as a result of different soil properties. Three separate simulation types were considered. The base case assumed spatially homogeneous soil texture and initial soil moisture. The second case assumed variable soil texture and constant initial soil moisture, while the third case allowed for both variable soil texture and initial soil moisture. The simulation domain was further divided into four geographically distinct regions. It is concluded there is a more dramatic impact on thermodynamic variables (surface temperature and dewpoint) than on surface winds, and a more pronounced variability in results during the summer period. While no obvious trends in surface winds or dewpoint temperature were found relative to observations covering all regions and times, improvement in surface temperatures in most regions and time periods was generally seen with the incorporation of variable soil texture and initial soil moisture.

  7. Species distribution models predict temporal but not spatial variation in forest growth.

    Science.gov (United States)

    van der Maaten, Ernst; Hamann, Andreas; van der Maaten-Theunissen, Marieke; Bergsma, Aldo; Hengeveld, Geerten; van Lammeren, Ron; Mohren, Frits; Nabuurs, Gert-Jan; Terhürne, Renske; Sterck, Frank

    2017-04-01

    Bioclimate envelope models have been widely used to illustrate the discrepancy between current species distributions and their potential habitat under climate change. However, the realism and correct interpretation of such projections has been the subject of considerable discussion. Here, we investigate whether climate suitability predictions correlate to tree growth, measured in permanent inventory plots and inferred from tree-ring records. We use the ensemble classifier RandomForest and species occurrence data from ~200,000 inventory plots to build species distribution models for four important European forestry species: Norway spruce, Scots pine, European beech, and pedunculate oak. We then correlate climate-based habitat suitability with volume measurements from ~50-year-old stands, available from ~11,000 inventory plots. Secondly, habitat projections based on annual historical climate are compared with ring width from ~300 tree-ring chronologies. Our working hypothesis is that habitat suitability projections from species distribution models should to some degree be associated with temporal or spatial variation in these growth records. We find that the habitat projections are uncorrelated with spatial growth records (inventory plot data), but they do predict interannual variation in tree-ring width, with an average correlation of .22. Correlation coefficients for individual chronologies range from values as high as .82 or as low as -.31. We conclude that tree responses to projected climate change are highly site-specific and that local suitability of a species for reforestation is difficult to predict. That said, projected increase or decrease in climatic suitability may be interpreted as an average expectation of increased or reduced growth over larger geographic scales.

  8. Modeling of Spatial and Temporal Variations of Phosphorous Cycling in Tree Islands of the Everglades

    Science.gov (United States)

    Lago, M.; Miralles-Wilhelm, F. R.

    2008-05-01

    A model to study the temporal and spatial variations on the phosphorous cycle around tree islands in Shark River Slough in the Everglades has been developed. It is based in a conceptual model that considers the convective and diffusive transport of dissolved phosphorous, adsorption on to soil, input from rainfall and animal activity, and the phosphorous cycle in biomass that includes uptake, release as litter, transport as suspended litter and release from the decomposition of the deposited litter. The developed model solved governing equations for water, phosphorous and biomass balances. The parameterization of the model was conducted by using the data collected in three tree islands of Shark River Slough, the time series data downloaded mainly from SFWMD's DBHYDRO, among other parameters reported the literature. The model was calibrated in three stages. Initially, Manning coefficients were adjusted from surface water velocity data. Then, calibration of several groundwater flow parameters was performed from water table data collected at wells by. Finally, the phosphorous input rate from animal activity and the initial concentration of phosphorous were calibrated. This study concluded that an external input rate of Phosphorous (e.g. from animal activity) is necessary to maintain the phosphorous levels in the areas around the head of the tree islands, to counteract losses from rainfall driven transport and suspended litter transport. This result points to the importance of the preservation of the wading birds and other wild life forms in the Everglades. The model also suggests an explanation for the sawgrass die-off events observed in the Everglades as well as a cyclic succession between marsh and tall sawgrass.

  9. Model-assisted analysis of spatial and temporal variations in fruit temperature and transpiration highlighting the role of fruit development.

    Directory of Open Access Journals (Sweden)

    Thibault Nordey

    Full Text Available Fruit physiology is strongly affected by both fruit temperature and water losses through transpiration. Fruit temperature and its transpiration vary with environmental factors and fruit characteristics. In line with previous studies, measurements of physical and thermal fruit properties were found to significantly vary between fruit tissues and maturity stages. To study the impact of these variations on fruit temperature and transpiration, a modelling approach was used. A physical model was developed to predict the spatial and temporal variations of fruit temperature and transpiration according to the spatial and temporal variations of environmental factors and thermal and physical fruit properties. Model predictions compared well to temperature measurements on mango fruits, making it possible to accurately simulate the daily temperature variations of the sunny and shaded sides of fruits. Model simulations indicated that fruit development induced an increase in both the temperature gradient within the fruit and fruit water losses, mainly due to fruit expansion. However, the evolution of fruit characteristics has only a very slight impact on the average temperature and the transpiration per surface unit. The importance of temperature and transpiration gradients highlighted in this study made it necessary to take spatial and temporal variations of environmental factors and fruit characteristics into account to model fruit physiology.

  10. Assessing effects of variation in global climate data sets on spatial predictions from climate envelope models

    Science.gov (United States)

    Romanach, Stephanie; Watling, James I.; Fletcher, Robert J.; Speroterra, Carolina; Bucklin, David N.; Brandt, Laura A.; Pearlstine, Leonard G.; Escribano, Yesenia; Mazzotti, Frank J.

    2014-01-01

    Climate change poses new challenges for natural resource managers. Predictive modeling of species–environment relationships using climate envelope models can enhance our understanding of climate change effects on biodiversity, assist in assessment of invasion risk by exotic organisms, and inform life-history understanding of individual species. While increasing interest has focused on the role of uncertainty in future conditions on model predictions, models also may be sensitive to the initial conditions on which they are trained. Although climate envelope models are usually trained using data on contemporary climate, we lack systematic comparisons of model performance and predictions across alternative climate data sets available for model training. Here, we seek to fill that gap by comparing variability in predictions between two contemporary climate data sets to variability in spatial predictions among three alternative projections of future climate. Overall, correlations between monthly temperature and precipitation variables were very high for both contemporary and future data. Model performance varied across algorithms, but not between two alternative contemporary climate data sets. Spatial predictions varied more among alternative general-circulation models describing future climate conditions than between contemporary climate data sets. However, we did find that climate envelope models with low Cohen's kappa scores made more discrepant spatial predictions between climate data sets for the contemporary period than did models with high Cohen's kappa scores. We suggest conservation planners evaluate multiple performance metrics and be aware of the importance of differences in initial conditions for spatial predictions from climate envelope models.

  11. Analyzing Spatial and Temporal Variation in Precipitation Estimates in a Coupled Model

    Science.gov (United States)

    Tomkins, C. D.; Springer, E. P.; Costigan, K. R.

    2001-12-01

    the LADHS and RAMS cumulative precipitation reveal a disassociation over time, with R equal to 0.74 at day eight and R equal to 0.52 at day 31. Linear correlation coefficients (Pearson) returned a stronger initial correlation of 0.97, decreasing to 0.68. The standard deviations for the 2500 LADHS cells underlying each 5km RAMS cell range from 8 mm to 695 mm in the Sangre de Cristo Mountains and 2 mm to 112 mm in the San Luis Valley. Comparatively, the standard deviations of the RAMS estimates in these regions are 247 mm and 30 mm respectively. The LADHS standard deviations provide a measure of the variability introduced through the downscaling routine, which exceeds RAMS regional variability by a factor of 2 to 4. The coefficient of variation for the average LADHS grid cell values and the RAMS cell values in the Sangre de Cristo Mountains are 0.66 and 0.27, respectively, and 0.79 and 0.75 in the San Luis Valley. The coefficients of variation evidence the uniformity of the higher precipitation estimates in the mountains, especially for RAMS, and also the lower means and variability found in the valley. Additionally, Kolmogorov-Smirnov tests indicate clear spatial and temporal differences in mean simulated precipitation across the grid.

  12. Modelling of spatial variation of floor eggs in an aviary house for laying hens

    NARCIS (Netherlands)

    Vroegindeweij, B.A.; Henten, van E.J.; Willigenburg, van L.G.; Groot Koerkamp, P.W.G.

    2013-01-01

    A problem in loose housing systems for layers is laying eggs on the floor, which need manual collection. To automate this, it is desired to know the location of floor eggs for planning a collection path. as this information is not available, we constructed a spatial model to indicate the probability

  13. Spatial Variation of Pressure in the Lyophilization Product Chamber Part 1: Computational Modeling.

    Science.gov (United States)

    Ganguly, Arnab; Varma, Nikhil; Sane, Pooja; Bogner, Robin; Pikal, Michael; Alexeenko, Alina

    2017-04-01

    The flow physics in the product chamber of a freeze dryer involves coupled heat and mass transfer at different length and time scales. The low-pressure environment and the relatively small flow velocities make it difficult to quantify the flow structure experimentally. The current work presents the three-dimensional computational fluid dynamics (CFD) modeling for vapor flow in a laboratory scale freeze dryer validated with experimental data and theory. The model accounts for the presence of a non-condensable gas such as nitrogen or air using a continuum multi-species model. The flow structure at different sublimation rates, chamber pressures, and shelf-gaps are systematically investigated. Emphasis has been placed on accurately predicting the pressure variation across the subliming front. At a chamber set pressure of 115 mtorr and a sublimation rate of 1.3 kg/h/m(2), the pressure variation reaches about 9 mtorr. The pressure variation increased linearly with sublimation rate in the range of 0.5 to 1.3 kg/h/m(2). The dependence of pressure variation on the shelf-gap was also studied both computationally and experimentally. The CFD modeling results are found to agree within 10% with the experimental measurements. The computational model was also compared to analytical solution valid for small shelf-gaps. Thus, the current work presents validation study motivating broader use of CFD in optimizing freeze-drying process and equipment design.

  14. Does spatial variation in environmental conditions affect recruitment? A study using a 3-D model of Peruvian anchovy

    Science.gov (United States)

    Xu, Yi; Rose, Kenneth A.; Chai, Fei; Chavez, Francisco P.; Ayón, Patricia

    2015-11-01

    We used a 3-dimensional individual-based model (3-D IBM) of Peruvian anchovy to examine how spatial variation in environmental conditions affects larval and juvenile growth and survival, and recruitment. Temperature, velocity, and phytoplankton and zooplankton concentrations generated from a coupled hydrodynamic Nutrients-Phytoplankton-Zooplankton-Detritus (NPZD) model, mapped to a three dimensional rectangular grid, were used to simulate anchovy populations. The IBM simulated individuals as they progressed from eggs to recruitment at 10 cm. Eggs and yolk-sac larvae were followed hourly through the processes of development, mortality, and movement (advection), and larvae and juveniles were followed daily through the processes of growth, mortality, and movement (advection plus behavior). A bioenergetics model was used to grow larvae and juveniles. The NPZD model provided prey fields which influence both food consumption rate as well as behavior mediated movement with individuals going to grids cells having optimal growth conditions. We compared predicted recruitment for monthly cohorts for 1990 through 2004 between the full 3-D IBM and a point (0-D) model that used spatially-averaged environmental conditions. The 3-D and 0-D versions generated similar interannual patterns in monthly recruitment for 1991-2004, with the 3-D results yielding consistently higher survivorship. Both versions successfully captured the very poor recruitment during the 1997-1998 El Niño event. Higher recruitment in the 3-D simulations was due to higher survival during the larval stage resulting from individuals searching for more favorable temperatures that lead to faster growth rates. The strong effect of temperature was because both model versions provided saturating food conditions for larval and juvenile anchovies. We conclude with a discussion of how explicit treatment of spatial variation affected simulated recruitment, other examples of fisheries modeling analyses that have used a

  15. Artificial Neural Network Modeling for Spatial and Temporal Variations of Pore-Water Pressure Responses to Rainfall

    Directory of Open Access Journals (Sweden)

    M. R. Mustafa

    2015-01-01

    Full Text Available Knowledge of spatial and temporal variations of soil pore-water pressure in a slope is vital in hydrogeological and hillslope related processes (i.e., slope failure, slope stability analysis, etc.. Measurements of soil pore-water pressure data are challenging, expensive, time consuming, and difficult task. This paper evaluates the applicability of artificial neural network (ANN technique for modeling soil pore-water pressure variations at multiple soil depths from the knowledge of rainfall patterns. A multilayer perceptron neural network model was constructed using Levenberg-Marquardt training algorithm for prediction of soil pore-water pressure variations. Time series records of rainfall and pore-water pressures at soil depth of 0.5 m were used to develop the ANN model. To investigate applicability of the model for prediction of spatial and temporal variations of pore-water pressure, the model was tested for the time series data of pore-water pressure at multiple soil depths (i.e., 0.5 m, 1.1 m, 1.7 m, 2.3 m, and 2.9 m. The performance of the ANN model was evaluated by root mean square error, mean absolute error, coefficient of correlation, and coefficient of efficiency. The results revealed that the ANN performed satisfactorily implying that the model can be used to examine the spatial and temporal behavior of time series of pore-water pressures with respect to multiple soil depths from knowledge of rainfall patterns and pore-water pressure with some antecedent conditions.

  16. Non-linear regression model for spatial variation in precipitation chemistry for South India

    Science.gov (United States)

    Siva Soumya, B.; Sekhar, M.; Riotte, J.; Braun, Jean-Jacques

    Chemical composition of rainwater changes from sea to inland under the influence of several major factors - topographic location of area, its distance from sea, annual rainfall. A model is developed here to quantify the variation in precipitation chemistry under the influence of inland distance and rainfall amount. Various sites in India categorized as 'urban', 'suburban' and 'rural' have been considered for model development. pH, HCO 3, NO 3 and Mg do not change much from coast to inland while, SO 4 and Ca change is subjected to local emissions. Cl and Na originate solely from sea salinity and are the chemistry parameters in the model. Non-linear multiple regressions performed for the various categories revealed that both rainfall amount and precipitation chemistry obeyed a power law reduction with distance from sea. Cl and Na decrease rapidly for the first 100 km distance from sea, then decrease marginally for the next 100 km, and later stabilize. Regression parameters estimated for different cases were found to be consistent ( R2 ˜ 0.8). Variation in one of the parameters accounted for urbanization. Model was validated using data points from the southern peninsular region of the country. Estimates are found to be within 99.9% confidence interval. Finally, this relationship between the three parameters - rainfall amount, coastline distance, and concentration (in terms of Cl and Na) was validated with experiments conducted in a small experimental watershed in the south-west India. Chemistry estimated using the model was in good correlation with observed values with a relative error of ˜5%. Monthly variation in the chemistry is predicted from a downscaling model and then compared with the observed data. Hence, the model developed for rain chemistry is useful in estimating the concentrations at different spatio-temporal scales and is especially applicable for south-west region of India.

  17. Multi-variate spatial explicit constraining of a large scale hydrological model

    Science.gov (United States)

    Rakovec, Oldrich; Kumar, Rohini; Samaniego, Luis

    2016-04-01

    model parameters leads to considerable changes in the partitioning of precipitation into runoff components, while maintaining total runoff estimates unaltered. Objective functions that take into account the spatial patters of GRACE estimates perform better than those constrained only against discharge. Improvements in parameter estimation based on multiple data sources will enhance the community efforts towards spatially consistent large scale seamless predictions. Reference: Rakovec, O., Kumar, R., Mai, J., Cuntz, M., Thober, S., Zink, M., Attinger, S., Schäfer, D., Schrön, M., Samaniego, L. (2016): Multiscale and multivariate evaluation of water fluxes and states over European river basins, J. Hydrometeorol., 17, 287-307, doi: 10.1175/JHM-D-15-0054.1.

  18. Species persistence in landscapes with spatial variation in habitat quality: a pair approximation model.

    Science.gov (United States)

    Liao, Jinbao; Li, Zhenqing; Hiebeler, David E; Iwasa, Yoh; Bogaert, Jan; Nijs, Ivan

    2013-10-21

    Habitat degradation has become a major threat to species persistence. Although several models have explicitly integrated habitat quality into metapopulation dynamics, we still lack knowledge of the spatial variability of species persistence which may result from the clustering of habitat patches of differing quality. Here we construct both pair approximation (PA) and cellular automaton (CA) models for species persistence in homogeneous versus heterogeneous landscapes. Heterogeneous landscapes are generated by varying the orthogonal-neighbour correlation between two different-quality habitats. In our simulations, the PA model exhibits similar population dynamics to the CA model, though it overestimates species persistence due to the doublet approximation neglecting correlation beyond nearest neighbours. Generally, landscape heterogeneity enhances species persistence relative to landscape homogeneity, especially with enlarging habitat-quality difference. This indicates that models based on homogeneous landscapes may overestimate species extinction rate. In heterogeneous landscapes, habitat clumping does not influence global dispersers because of random establishment, although it does promote the persistence of local dispersers, especially under severe habitat degradation. However, habitat configurational fragmentation improves the persistence of global dispersers that are highly sensitive to local crowding, probably by reducing density dependence, but this positive fragmentation effect on local dispersers is overshadowed by the stronger negative border effect on impeding local extension. Furthermore, increasing density dependence promotes the extinction risk of local dispersers, while global dispersers are not influenced. For conservation and habitat management, our results suggest that minimising random anthropogenic disturbance should take priority over increasing the connectivity of good-quality habitat, as random habitat degradation poses a more serious threat to

  19. Assessment of spatial variation in drinking water iodine and its implications for dietary intake: A new conceptual model for Denmark

    Energy Technology Data Exchange (ETDEWEB)

    Voutchkova, Denitza Dimitrova, E-mail: ddv@geo.au.dk [Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, DK-8000 Aarhus C (Denmark); Geological Survey of Denmark and Greenland (GEUS), Lyseng Allé 1, DK-8270 Højbjerg (Denmark); Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K (Denmark); Ernstsen, Vibeke [Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K (Denmark); Hansen, Birgitte; Sørensen, Brian Lyngby [Geological Survey of Denmark and Greenland (GEUS), Lyseng Allé 1, DK-8270 Højbjerg (Denmark); Zhang, Chaosheng [GIS Centre and School of Geography and Archaeology, National University of Ireland, Galway (Ireland); Kristiansen, Søren Munch [Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, DK-8000 Aarhus C (Denmark)

    2014-09-15

    Iodine is essential for human health. Many countries have therefore introduced universal salt iodising (USI) programmes to ensure adequate intake for the populations. However, little attention has been paid to subnational differences in iodine intake from drinking water caused by naturally occurring spatial variations. To address this issue, we here present the results of a Danish nationwide study of spatial trends of iodine in drinking water and the relevance of these trends for human dietary iodine intake. The data consist of treated drinking water samples from 144 waterworks, representing approx. 45% of the groundwater abstraction for drinking water supply in Denmark. The samples were analysed for iodide, iodate, total iodine (TI) and other major and trace elements. The spatial patterns were investigated with Local Moran's I. TI ranges from < 0.2 to 126 μg L{sup −1} (mean 14.4 μg L{sup −1}, median 11.9 μg L{sup −1}). Six speciation combinations were found. Half of the samples (n = 71) contain organic iodine; all species were detected in approx. 27% of all samples. The complex spatial variation is attributed both to the geology and the groundwater treatment. TI > 40 μg L{sup −1} originates from postglacial marine and glacial meltwater sand and from Campanian–Maastrichtian chalk aquifers. The estimated drinking water contribution to human intake varies from 0% to > 100% of the WHO recommended daily iodine intake for adults and from 0% to approx. 50% for adolescents. The paper presents a new conceptual model based on the observed clustering of high or low drinking-water iodine concentrations, delimiting zones with potentially deficient, excessive or optimal iodine status. Our findings suggest that the present coarse-scale nationwide programme for monitoring the population's iodine status may not offer a sufficiently accurate picture. Local variations in drinking-water iodine should be mapped and incorporated into future adjustment of the

  20. Modelling spatial and temporal variations in the water quality of an artificial water reservoir in the semiarid Midwest of Argentina

    Energy Technology Data Exchange (ETDEWEB)

    Cid, Fabricio D., E-mail: fabricio.cid@gmail.com [Laboratory of Biology ' Prof. E. Caviedes Codelia' , Facultad de Ciencias Humanas, Universidad Nacional de San Luis, San Luis (Argentina); Laboratory of Integrative Biology, Institute for Multidisciplinary Research in Biology (IMIBIO-SL), Consejo Nacional de Investigaciones Cientificas y Tecnicas, San Luis (Argentina); Department of Biochemistry and Biological Sciences, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, San Luis (Argentina); Anton, Rosa I. [Department of Analytical Chemistry, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, San Luis (Argentina); Pardo, Rafael; Vega, Marisol [Department of Analytical Chemistry, Facultad de Ciencias, Universidad de Valladolid, Valladolid (Spain); Caviedes-Vidal, Enrique [Laboratory of Biology ' Prof. E. Caviedes Codelia' , Facultad de Ciencias Humanas, Universidad Nacional de San Luis, San Luis (Argentina); Laboratory of Integrative Biology, Institute for Multidisciplinary Research in Biology (IMIBIO-SL), Consejo Nacional de Investigaciones Cientificas y Tecnicas, San Luis (Argentina); Department of Biochemistry and Biological Sciences, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, San Luis (Argentina)

    2011-10-31

    Highlights: {yields} Water quality of an Argentinean reservoir has been investigated by N-way PCA. {yields} PARAFAC mode modelled spatial and seasonal variations of water composition. {yields} Two factors related with organic and lead pollution have been identified. {yields} The most polluted areas of the reservoir were located, and polluting sources identified. - Abstract: Temporal and spatial patterns of water quality of an important artificial water reservoir located in the semiarid Midwest of Argentina were investigated using chemometric techniques. Surface water samples were collected at 38 points of the water reservoir during eleven sampling campaigns between October 1998 and June 2000, covering the warm wet season and the cold dry season, and analyzed for dissolved oxygen (DO), conductivity, pH, ammonium, nitrate, nitrite, total dissolved solids (TDS), alkalinity, hardness, bicarbonate, chloride, sulfate, calcium, magnesium, fluoride, sodium, potassium, iron, aluminum, silica, phosphate, sulfide, arsenic, chromium, lead, cadmium, chemical oxygen demand (COD), biochemical oxygen demand (BOD), viable aerobic bacteria (VAB) and total coliform bacteria (TC). Concentrations of lead, ammonium, nitrite and coliforms were higher than the maximum allowable limits for drinking water in a large proportion of the water samples. To obtain a general representation of the spatial and temporal trends of the water quality parameters at the reservoir, the three-dimensional dataset (sampling sites x parameters x sampling campaigns) has been analyzed by matrix augmentation principal component analysis (MA-PCA) and N-way principal component analysis (N-PCA) using Tucker3 and PARAFAC (Parallel Factor Analysis) models. MA-PCA produced a component accounting for the general behavior of parameters associated with organic pollution. The Tucker3 models were not appropriate for modelling the water quality dataset. The two-factor PARAFAC model provided the best picture to understand the

  1. Spherical deconvolution of multichannel diffusion MRI data with non-Gaussian noise models and total variation spatial regularization

    CERN Document Server

    Canales-Rodríguez, Erick J; Sotiropoulos, Stamatios N; Caruyer, Emmanuel; Aja-Fernández, Santiago; Radua, Joaquim; Mendizabal, Yosu Yurramendi; Iturria-Medina, Yasser; Melie-García, Lester; Alemán-Gómez, Yasser; Thiran, Jean-Philippe; Sarró, Salvador; Pomarol-Clotet, Edith; Salvador, Raymond

    2014-01-01

    Due to a higher capability in resolving white matter fiber crossings, Spherical Deconvolution (SD) methods have become very popular in brain fiber-tracking applications. However, while some of these estimation algorithms assume a central Gaussian distribution for the MRI noise, its real distribution is known to be non-Gaussian and to depend on many factors such as the number of coils and the methodology used to combine multichannel signals. Indeed, the two prevailing methods for multichannel signal combination lead to noise patterns better described by Rician and noncentral Chi distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique intended to deal with realistic MRI noise. The algorithm relies on a maximum a posteriori formulation based on Rician and noncentral Chi likelihood models and includes a total variation (TV) spatial regularization term. By means of a synthetic phantom contaminated with noise mimicking patterns generated by data processing in mu...

  2. Effects of small spatial variation of the reproduction rate in a two species competition model

    Directory of Open Access Journals (Sweden)

    Georg Hetzer

    2010-11-01

    Full Text Available Of concern is the effect of a small spatially inhomogeneous perturbation of the reproduction rate of the first species in a two-species Lotka-Volterra competition-diffusion problem with spatially homogeneous reaction terms. Apart from this perturbation and the diffusion rates, the two species are assumed to be identical. Our main result shows that the first species can always invade, whereas the second species can only invade under certain conditions which yield uniform persistence of both species. The proof relies on comparison techniques and properties of the principal eigenvalue of reaction-diffusion equations.

  3. Modelling spatial and temporal variations in the water quality of an artificial water reservoir in the semiarid midwest of Argentina.

    Science.gov (United States)

    Cid, Fabricio D; Antón, Rosa I; Pardo, Rafael; Vega, Marisol; Caviedes-Vidal, Enrique

    2011-10-31

    Temporal and spatial patterns of water quality of an important artificial water reservoir located in the semiarid Midwest of Argentina were investigated using chemometric techniques. Surface water samples were collected at 38 points of the water reservoir during eleven sampling campaigns between October 1998 and June 2000, covering the warm wet season and the cold dry season, and analyzed for dissolved oxygen (DO), conductivity, pH, ammonium, nitrate, nitrite, total dissolved solids (TDS), alkalinity, hardness, bicarbonate, chloride, sulfate, calcium, magnesium, fluoride, sodium, potassium, iron, aluminum, silica, phosphate, sulfide, arsenic, chromium, lead, cadmium, chemical oxygen demand (COD), biochemical oxygen demand (BOD), viable aerobic bacteria (VAB) and total coliform bacteria (TC). Concentrations of lead, ammonium, nitrite and coliforms were higher than the maximum allowable limits for drinking water in a large proportion of the water samples. To obtain a general representation of the spatial and temporal trends of the water quality parameters at the reservoir, the three-dimensional dataset (sampling sites×parameters×sampling campaigns) has been analyzed by matrix augmentation principal component analysis (MA-PCA) and N-way principal component analysis (N-PCA) using Tucker3 and PARAFAC (Parallel Factor Analysis) models. MA-PCA produced a component accounting for the general behavior of parameters associated with organic pollution. The Tucker3 models were not appropriate for modelling the water quality dataset. The two-factor PARAFAC model provided the best picture to understand the spatial and temporal variation of the water quality parameters of the reservoir. The first PARAFAC factor contains useful information regarding the relation of organic pollution with seasonality, whereas the second factor also encloses information concerning lead pollution. The most polluted areas in the reservoir and the polluting sources were identified by plotting PARAFAC

  4. A variation pixels identification method based on kernel spatial attraction model and local entropy for robust endmember extraction

    Institute of Scientific and Technical Information of China (English)

    赵春晖; 田明华; 齐滨; 王玉磊

    2016-01-01

    A variation pixels identification method was proposed aiming at depressing the effect of variation pixels, which dilates the theoretical hyperspectral data simplex and misguides volume evaluation of the simplex. With integration of both spatial and spectral information, this method quantitatively defines a variation index for every pixel. The variation index is proportional to pixels local entropy but inversely proportional to pixels kernel spatial attraction. The number of pixels removed was modulated by an artificial threshold factorα. Two real hyperspectral data sets were employed to examine the endmember extraction results. The reconstruction errors of preprocessing data as opposed to the result of original data were compared. The experimental results show that the number of distinct endmembers extracted has increased and the reconstruction error is greatly reduced. 100% is an optional value for the threshold factorα when dealing with no prior knowledge hyperspectral data.

  5. Spatial and temporal variations in ammonia emissions - a freely accessible model code for Europe

    DEFF Research Database (Denmark)

    Skjøth, Carsten Ambelas; Geels, Camilla; Berge, H.

    2011-01-01

    on these input data improves the NH3 calculations in a CTM model when the results are compared with calculations obtained by traditional methods in emission handling. It is also shown how input data can be modified over a specific target region resulting in even further improvement in performance over......Deriving a parameterisation of ammonia emissions for use in chemistry-transport models (CTMs) is a complex problem as the emission varies locally as a result of local climate and local agricultural management. In current CTMs such factors are generally not taken into account. This paper...... demonstrates how local climate and local management can be accounted for in CTMs by applying a modular approach for deriving data as input to a dynamic ammonia emission model for Europe. Default data are obtained from information in the RAINS system, and it is demonstrated how this dynamic emission model based...

  6. Spatial Variations of Fundamental Constants

    CERN Document Server

    Barrow, John D; Barrow, John D.; Toole, Chris O'

    1999-01-01

    We show that observational limits on the possible time variation of constants of Nature are significantly affected by allowing for both space and time variation. Bekenstein's generalisation of Maxwell's equations to allow for cosmological variation of $alpha$ is investigated in a universe containing spherically symmetric inhomogeneities. The time variation of $alpha$ is determined by the local matter density and hence limits obtained in high-density geophysical enviroments are far more constraining than those obtained at high redshift. This new feature is expected to be a property of a wide class of theories for the variation of constants.

  7. Seasonal and spatial variations of 17Oexcess and dexcess in Antarctic precipitation: Insights from an intermediate complexity isotope model

    Science.gov (United States)

    Schoenemann, Spruce W.; Steig, Eric J.

    2016-10-01

    An intermediate complexity model (ICM) is used to investigate the sensitivity of water isotope ratios in precipitation, including 17Oexcess, to climate variations in the Southern Hemisphere. The ICM is forced with boundary conditions from seasonal National Centers for Environmental Prediction/Department of Energy II reanalysis data. Perturbations to the surface temperature and humidity fields are used to investigate the isotopic sensitivity. The response of 17Oexcess to a uniform temperature change is insignificant over the ocean, while there is a large magnitude response over the ice sheet, particularly in East Antarctica. A decrease of ocean surface relative humidity produces increased 17Oexcess and dexcess, with a coherent response over both the ocean and Antarctica. For interior East Antarctica, the model simulates a seasonal cycle in 17Oexcess that is positively correlated with δ18O and of large magnitude ( 50 per meg), consistent with the observations from Vostok. The seasonal cycle in 17Oexcess for interior West Antarctica is predicted to be considerably smaller in magnitude (12 per meg), and is negatively correlated with δ18O, consistent with new data from a firn core near the West Antarctic Ice Sheet Divide site. Over the ocean, the ICM predicts much smaller seasonal cycles in 17Oexcess. Oceanic source changes (i.e., humidity) are insufficient to explain the amplitude of the simulated seasonal cycle over the Antarctic continent. Spatial differences in the seasonal response of 17Oexcess to local temperature reflect the balance of equilibrium and kinetic fractionation during snow formation.

  8. Spatial variation in population structure and its relation to movement and the potential for dispersal in a model intertidal invertebrate.

    Directory of Open Access Journals (Sweden)

    Trevor T Bringloe

    Full Text Available Dispersal, the movement of an individual away from its natal or breeding ground, has been studied extensively in birds and mammals to understand the costs and benefits of movement behavior. Whether or not invertebrates disperse in response to such attributes as habitat quality or density of conspecifics remains uncertain, due in part to the difficulties in marking and recapturing invertebrates. In the upper Bay of Fundy, Canada, the intertidal amphipod Corophium volutator swims at night around the new or full moon. Furthermore, this species is regionally widespread across a large spatial scale with site-to-site variation in population structure. Such variation provides a backdrop against which biological determinants of dispersal can be investigated. We conducted a large-scale study at nine mudflats, and used swimmer density, sampled using stationary plankton nets, as a proxy for dispersing individuals. We also sampled mud residents using sediment cores over 3 sampling rounds (20-28 June, 10-17 July, 2-11 August 2010. Density of swimmers was most variable at the largest spatial scales, indicating important population-level variation. The smallest juveniles and large juveniles or small adults (particularly females were consistently overrepresented as swimmers. Small juveniles swam at most times and locations, whereas swimming of young females decreased with increasing mud presence of young males, and swimming of large juveniles decreased with increasing mud presence of adults. Swimming in most stages increased with density of mud residents; however, proportionally less swimming occurred as total mud resident density increased. We suggest small juveniles move in search of C. volutator aggregations which possibly act as a proxy for better habitat. We also suggest large juveniles and small adults move if potential mates are limiting. Future studies can use sampling designs over large spatial scales with varying population structure to help

  9. Spatial analysis of rainfall variation using variogram model parameters of X-band radar images in a small mountainous catchment

    Science.gov (United States)

    Guardiola-Albert, Carolina; Díez-Herrero, Andrés; Bodoque, José M.; Bermejo, Marcos; Rivero-Honegger, Carlos; Yagüe, Carlos; Monjo, Robert; Tapiador, Francisco J.

    2016-04-01

    The present study deals the rainfall spatial variability of a small mountainous catchment, which includes the spatial distribution and variability of convective and stratiform events. This work focuses on the precipitation events with hydrological response in Venero-Claro Basin (Avila, Spain). In this basin of 15 square kilometers, flood events of different magnitudes have been often registered. Therefore, any improvement in understanding rainfall characteristics in the area can be of special importance in rainfall estimation and hence to calibrate and validate hydrological models. These enhancements imply more objectivity of risk studies and more predictive and preventive capacity. To separate events by origin it has been used the dimensionless index defined by Monjo (2015), according to the relative temporal distribution of maximum intensities. The main advantages of this method are that it does not require thresholds, so it can be applied for each rain gauge. The geostatistical variogram tool is used to quantify the spatial characteristics of both kinds of events. Hourly rainfall accumulations over the area are computed with observations from one of the 5 existing X-band radar in Spain and 7 rain gauges located in the zone. For each hour the rainfall variogram model has been fitted with the aid of the X-band radar images. Valuable information is extracted from the stratiform and convective ensembles of variogram models. The variogram model parameters are analyzed to determine characteristics of spatial continuity that differentiates stratiform and convective events, and quartiles of sills and ranges in both ensembles are compared.

  10. Spatial Variations in Vitreous Oxygen Consumption.

    Science.gov (United States)

    Murali, Karthik; Kang, Dongyang; Nazari, Hossein; Scianmarello, Nicholas; Cadenas, Enrique; Tai, Yu-Chong; Kashani, Amir; Humayun, Mark

    2016-01-01

    We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M(-1) s(-1) ± 0.708 M(-1) s(-1) (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration.

  11. Assessment of the Spatial and Temporal Variations of Water Quality for Agricultural Lands with Crop Rotation in China by Using a HYPE Model.

    Science.gov (United States)

    Yin, Yunxing; Jiang, Sanyuan; Pers, Charlotta; Yang, Xiaoying; Liu, Qun; Yuan, Jin; Yao, Mingxing; He, Yi; Luo, Xingzhang; Zheng, Zheng

    2016-03-18

    Many water quality models have been successfully used worldwide to predict nutrient losses from anthropogenically impacted catchments, but hydrological and nutrient simulations with limited data are difficult considering the transfer of model parameters and complication of model calibration and validation. This study aims: (i) to assess the performance capabilities of a new and relatively more advantageous model, namely, Hydrological Predictions for the Environment (HYPE), that simulates stream flow and nutrient load in agricultural areas by using a multi-site and multi-objective parameter calibration method and (ii) to investigate the temporal and spatial variations of total nitrogen (TN) and total phosphorous (TP) concentrations and loads with crop rotation by using the model for the first time. A parameter estimation tool (PEST) was used to calibrate parameters. Results show that the parameters related to the effective soil porosity were highly sensitive to hydrological modeling. N balance was largely controlled by soil denitrification processes. P balance was influenced by the sedimentation rate and production/decay of P in rivers and lakes. The model reproduced the temporal and spatial variations of discharge and TN/TP relatively well in both calibration (2006-2008) and validation (2009-2010) periods. Among the obtained data, the lowest Nash-Suttclife efficiency of discharge, daily TN load, and daily TP load were 0.74, 0.51, and 0.54, respectively. The seasonal variations of daily TN concentrations in the entire simulation period were insufficient, indicated that crop rotation changed the timing and amount of N output. Monthly TN and TP simulation yields revealed that nutrient outputs were abundant in summer in terms of the corresponding discharge. The area-weighted TN and TP load annual yields in five years showed that nutrient loads were extremely high along Hong and Ru rivers, especially in agricultural lands.

  12. Sources of spatial variation in methane emission from mires in northern Sweden: A mechanistic approach in statistical modeling

    Science.gov (United States)

    Granberg, Gunnar; Mikkelä, Catharina; Sundh, Ingvar; Svensson, Bo H.; Nilsson, Mats

    1997-06-01

    Methane emissions from six mires in northern Sweden were measured using a closed chamber technique during the frost free season in 1992. The average methane flux over the measurement period, calculated either for each mire or for different plant communities within one mire, ranged from 9 to 83 mg CH4 m-2 d-1. The emission rate on each occasion was related to physical and chemical environmental variables, both in a general data set for all mires (n = 836) and in subdata sets for individual mires, using multiple linear regression. The variables with significant contributions to the models were water table, standing water above the vegetation surface, peat temperatures, and principal components of the near infrared reflectance spectra of peat samples reflecting variations in organic chemical composition. To account for the actual contribution of methane production and methane oxidation, variables describing the active parts of the vertically distributed potentials of methane production or oxidation were constructed. The interaction terms between these variables, respectively, describing the active proportion of methanogens and methanotrophs, and the temperature values representing the anoxic and oxic parts of the profile were significantly correlated to the methane emission rate; positively for the production zone and negatively for the consumption zone. By using this mechanistic approach, a significant temperature effect in both the methane production and consumption zone was detected. These constructed temperature variables explain 21% of the variance in the logarithmically transformed methane fluxes using the entire data set (n = 836) but only 5% of the variance using peat temperatures from fixed depths. Adding variables describing the organic chemical composition of the peat to the models improved the predictability in 10 of the 11 model sets tested, decreasing the unexplained variance by maximally 50% for a poor fen community model and increasing R2 from 0.40 to

  13. Spatial cluster modelling

    CERN Document Server

    Lawson, Andrew B

    2002-01-01

    Research has generated a number of advances in methods for spatial cluster modelling in recent years, particularly in the area of Bayesian cluster modelling. Along with these advances has come an explosion of interest in the potential applications of this work, especially in epidemiology and genome research. In one integrated volume, this book reviews the state-of-the-art in spatial clustering and spatial cluster modelling, bringing together research and applications previously scattered throughout the literature. It begins with an overview of the field, then presents a series of chapters that illuminate the nature and purpose of cluster modelling within different application areas, including astrophysics, epidemiology, ecology, and imaging. The focus then shifts to methods, with discussions on point and object process modelling, perfect sampling of cluster processes, partitioning in space and space-time, spatial and spatio-temporal process modelling, nonparametric methods for clustering, and spatio-temporal ...

  14. Standing variation in spatially growing populations

    Science.gov (United States)

    Fusco, Diana; Gralka, Matti; Kayser, Jona; Hallatschek, Oskar

    Patterns of genetic diversity not only reflect the evolutionary history of a species but they can also determine the evolutionary response to environmental change. For instance, the standing genetic diversity of a microbial population can be key to rescue in the face of an antibiotic attack. While genetic diversity is in general shaped by both demography and evolution, very little is understood when both factors matter, as e.g. for biofilms with pronounced spatial organization. Here, we quantitatively explore patterns of genetic diversity by using microbial colonies and well-mixed test tube populations as antipodal model systems with extreme and very little spatial structure, respectively. We find that Eden model simulations and KPZ theory can remarkably reproduce the genetic diversity in microbial colonies obtained via population sequencing. The excellent agreement allows to draw conclusions on the resilience of spatially-organized populations and to uncover new strategies to contain antibiotic resistance.

  15. Storm surge variational assimilation model

    Directory of Open Access Journals (Sweden)

    Shi-li HUANG

    2010-06-01

    Full Text Available To eliminate errors caused by uncertainty of parameters and further improve capability of storm surge forecasting, the variational data assimilation method is applied to the storm surge model based on unstructured grid with high spatial resolution. The method can effectively improve the forecasting accuracy of storm surge induced by typhoon through controlling wind drag force coefficient parameter. The model is first theoretically validated with synthetic data. Then, the real storm surge process induced by the TC 0515 typhoon is forecasted by the variational data assimilation model, and results show the feasibility of practical application.

  16. A variational image restoration with spatially varying noise

    Science.gov (United States)

    Bao, Zheng; Bai, Hua; Liu, Ruihua; Shen, Chaomin

    2008-10-01

    The noise in natural images sometimes changes according to imaging mechanism or local image information. This is called spatially varying noise. It is obvious that classical variational denoising algorithms such as the Rudin-Osher-Fatemi model are not suitable for this kind of noise. We propose a variational method to remove this spatially varying noise based on the estimation of local variance for a given image, such that high noise regions are smoothed meanwhile the textures and certain details in low noise regions are preserved. Moreover, we give the proof of existence of the minimizer of our proposed functional. The experimental results show visual improvement and high signal-to-noise ratio over other variational denoising models.

  17. Three-dimensional analytical model for the spatial variation of the foreshock electron distribution function - Systematics and comparisons with ISEE observations

    Science.gov (United States)

    Fitzenreiter, R. J.; Scudder, J. D.; Klimas, A. J.

    1990-01-01

    A model which is consistent with the solar wind and shock surface boundary conditions for the foreshock electron distribution in the absence of wave-particle effects is formulated for an arbitrary location behind the magnetic tangent to the earth's bow shock. Variations of the gyrophase-averaged velocity distribution are compared and contrasted with in situ ISEE observations. It is found that magnetic mirroring of solar wind electrons is the most important process by which nonmonotonic reduced electron distributions in the foreshock are produced. Leakage of particles from the magnetosheath is shown to be relatively unimportant in determining reduced distributions that are nonmonotonic. The two-dimensional distribution function off the magnetic field direction is the crucial contribution in producing reduced distributions which have beams. The time scale for modification of the electron velocity distribution in velocity space can be significantly influenced by steady state spatial gradients in the background imposed by the curved shock geometry.

  18. Modeling the temporal and spatial variations of the vertical structure of Jupiter's atmosphere using observations of the 3-0 hydrogen quadrupole lines

    Science.gov (United States)

    Cunningham, C. C.; Hunten, D. M.; Tomasko, M. G.

    1986-01-01

    An observational program was established in 1983 to monitor the spatial and temporal variations in the Jovian atmosphere over short and long time scales. The program involves tracking several different longitudes as they rotate around the planet from one limb to another. This tracking experiment was done at many different wavelengths including the 3-0 S(1) and S(0) hydrogen quadrupole lines as well as several broad band methane absorptions. The June 1983 hydrogen quadrupole data was reduced and equivalent widths were measured for approximately 25 east-west positions across the planet at 7 different latitudes for both wavelengths. The data for the South Tropical Zone (20 deg. S) was modeled extensively and the effects of the various model parameters on the value of the calculated equivalent widths of both lines was measured as a longitude rotated from the east (or morning) limb to the west (or evening) limb. The value of the equivalent width is also quite sensitive to the height of the NH3 cloud top and to the value used for the single scattering albedo. A combination of these parameters changing on a diurnal time scale could also explain these observations. This gradual increase from one limb to the other appears in the data for both the North and South Equatorial Belts as well as the equatorial region and the North Tropical Zone. Models that used only normal hydrogen and models that used only equilibrium hydrogen were studied.

  19. Modeling the Spatial and Temporal Variation of Monthly and Seasonal Precipitation on the Nevada Test Site and Vicinity, 1960-2006

    Science.gov (United States)

    Blainey, Joan B.; Webb, Robert H.; Magirl, Christopher S.

    2007-01-01

    The Nevada Test Site (NTS), located in the climatic transition zone between the Mojave and Great Basin Deserts, has a network of precipitation gages that is unusually dense for this region. This network measures monthly and seasonal variation in a landscape with diverse topography. Precipitation data from 125 climate stations on or near the NTS were used to spatially interpolate precipitation for each month during the period of 1960 through 2006 at high spatial resolution (30 m). The data were collected at climate stations using manual and/or automated techniques. The spatial interpolation method, applied to monthly accumulations of precipitation, is based on a distance-weighted multivariate regression between the amount of precipitation and the station location and elevation. This report summarizes the temporal and spatial characteristics of the available precipitation records for the period 1960 to 2006, examines the temporal and spatial variability of precipitation during the period of record, and discusses some extremes in seasonal precipitation on the NTS.

  20. Modeling spatial and temporal variations in temperature and salinity during stratification and overturn in Dexter Pit Lake, Tuscarora, Nevada, USA

    Science.gov (United States)

    Balistrieri, L.S.; Tempel, R.N.; Stillings, L.L.; Shevenell, L.A.

    2006-01-01

    This paper examines the seasonal cycling of temperature and salinity in Dexter pit lake in arid northern Nevada, and describes an approach for modeling the physical processes that operate in such systems. The pit lake contains about 596,200 m3 of dilute, near neutral (pHs 6.7-9) water. Profiles of temperature, conductivity, and selected element concentrations were measured almost monthly during 1999 and 2000. In winter (January-March), the pit lake was covered with ice and bottom water was warmer (5.3 ??C) with higher total dissolved solids (0.298 g/L) than overlying water (3.96 ??C and 0.241 g/L), suggesting inflow of warm (11.7 ??C) groundwater with a higher conductivity than the lake (657 versus 126-383 ??S/cm). Seasonal surface inflow due to spring snowmelt resulted in lower conductivity in the surface water (232-247 ??S/cm) relative to deeper water (315-318 ??S/cm). The pit lake was thermally stratified from late spring through early fall, and the water column turned over in late November (2000) or early December (1999). The pit lake is a mixture of inflowing surface water and groundwater that has subsequently been evapoconcentrated in the arid environment. Linear relationships between conductivity and major and some minor (B, Li, Sr, and U) ions indicate conservative mixing for these elements. Similar changes in the elevations of the pit lake surface and nearby groundwater wells during the year suggest that the pit lake is a flow-through system. This observation and geochemical information were used to configure an one-dimensional hydrodynamics model (Dynamic Reservoir Simulation Model or DYRESM) that predicts seasonal changes in temperature and salinity based on the interplay of physical processes, including heating and cooling (solar insolation, long and short wave radiation, latent, and sensible heat), hydrologic flow (inflow and outflow by surface and ground water, pumping, evaporation, and precipitation), and transfers of momentum (wind stirring

  1. Characterizing Subcore Heterogeneity: A New Analytical Model and Technique to Observe the Spatial Variation of Transverse Dispersion

    Science.gov (United States)

    Boon, Maartje; Niu, Ben; Krevor, Sam

    2015-04-01

    Transverse dispersion, the lateral spread of chemical components in an aqueous solution caused by small heterogeneities in a rock, plays an important role in spreading, mixing and reaction during flow through porous media. Conventionally, transverse dispersion has been determined with the use of an annular core device and concentration measurements of the effluent (Blackwell, 1962; Hassinger and Von Rosenberg, 1968) or concentration measurements at probe locations along the core (Han et al, 1985; Harleman and Rumer, 1963). Both methods were designed around an analytical model of the transport equations assuming a single constant for the transverse dispersion coefficient, which is used to analyse the experimental data. We have developed a new core flood test with the aim of characterising chemical transport and dispersion directly in three dimensions to (1) produce higher precision observations of transverse dispersion than has been possible before and (2) so that the effects of rock heterogeneity on transport can also be observed and summarised using statistical descriptions allowing for a more nuanced picture of transport than allowed by description with a single transverse dispersion coefficient. The dispersion of a NaI aqueous solution injected into a Berea sandstone rock core was visualised in 3D with the use of a medical x-ray CT scanner. A device consisting out of three annular regions was used for injection. Water was injected into the centre and outer annular region and a NaI aqueous solution was injected in the middle annular region. An analytical solution to the flow and transport equations for this new inlet configuration was derived to design the tests. The Berea sandstone core was 20 cm long and had a diameter of 7.62cm. The core flood experiments were carried out for Peclet nr 0.5 and Peclet nr 2. At steady state, x-ray images were taken every 0.2 cm along the core. This resulted in a high quality 3D digital data set of the concentration distribution

  2. Equilibrium models and variational inequalities

    CERN Document Server

    Konnov, Igor

    2007-01-01

    The concept of equilibrium plays a central role in various applied sciences, such as physics (especially, mechanics), economics, engineering, transportation, sociology, chemistry, biology and other fields. If one can formulate the equilibrium problem in the form of a mathematical model, solutions of the corresponding problem can be used for forecasting the future behavior of very complex systems and, also, for correcting the the current state of the system under control. This book presents a unifying look on different equilibrium concepts in economics, including several models from related sciences.- Presents a unifying look on different equilibrium concepts and also the present state of investigations in this field- Describes static and dynamic input-output models, Walras, Cassel-Wald, spatial price, auction market, oligopolistic equilibrium models, transportation and migration equilibrium models- Covers the basics of theory and solution methods both for the complementarity and variational inequality probl...

  3. The implications for dust emission modeling of spatial and vertical variations in horizontal dust flux and particle size in the Bodélé Depression, Northern Chad

    Science.gov (United States)

    Chappell, Adrian; Warren, Andrew; O'Donoghue, Alice; Robinson, Andrea; Thomas, Andrew; Bristow, Charlie

    2008-02-01

    The Bodélé Depression has been confirmed as the single largest source of atmospheric mineral dust on Earth. It is a distinctive source because of its large exposure of diatomite and the presence of mega-barchan dunes. Direct measurements of horizontal dust flux and particle size were made to investigate dust emission processes and for comparison with mechanisms of emission assumed in current dust models. More than 50 masts, with traps mounted on each, were located across and downwind of three barchans in 56 km2 study area of the eastern Bodélé. The size-distribution of surface material is bi-modal; there are many fine dust modes and a mixed mineralogy with a particle density three times smaller than quartz. Horizontal fluxes (up to 70 m above the playa) of particles, up to 1000 μm in diameter, are produced frequently from the accelerated flow over and around the barchans, even in below-threshold shear conditions on the diatomite playa. Our data on dust sizes do not conform to retrievals of dust size distributions from radiance measurements made in the same area. Dust emission models for the region may need to be revised to account for: saltators in the Bodélé, which are a mixture of quartz sand and diatomite flakes; the great spatial and vertical variation in the abundance, mass and density of dust and abraders; and the patterns of surface erodibility. All of these have important local effects on the vertical dust flux and its particle sizes.

  4. Modelling the Spatial-temporal Variation of Urban/peri-urban Forests and Their Ecosystem Services: a Case Study of North-West Sydney

    Science.gov (United States)

    Odeh, I. A.; Zou, X. L.

    2015-12-01

    In terms of total terrestrial sequestered carbon, the global soils and forests are recognized as the predominant C sinks. Even though urban forests stored a relatively small proportion of the total terrestrial C, they also provide other important ecosystem services such as improving air quality, cooling effect in buildings and aesthetics. Thus in view of these environmental services the quantification of urban tree is increasingly viewed as essential to the understanding of how these ecosystem services can be optimized. The aims of this paper are to: i) quantify the spatial-temporal distribution of urban forests in Northwest Sydney using remote sensing techniques; ii) determine the total urban C-storage over many decades; iii) apply UFORE model to estimate air pollutant removal ability of urban forest. The results revealed the estimated total trees in Northwest Sydney in 2011was approximately 2.3 million. These urban forests potentially store an estimated 1.3 million tons of carbon in various forms such as biomass, soil carbon, etc. The relative carbon sequestration rate of these trees was estimated to be about 20,500 tC/yr (equivalent to AUD 467,000/year). Furthermore, the results show that trees near buildings can potentially avoid AUD 12.9 million of energy cost every year and 70000 tons of carbon emission, the latter which is equivalent to additional savings of nearly AUD 1.6 million per year. We also estimated that urban forests in the study area could potentially remove about 44,600 tons of pollutants (mainly greenhouse gases) annually equivalent to a saving of about AUD 409 million per year. Thus the results reveal the spatial-temporal variation of urban vegetation in the last twenty year between 1991 and 2011. The study has showcased the importance and potential role of urban forests in preserving carbon and thus reducing GHG emissions into atmosphere. Furthermore, these results highlight the significant value of urban forests in term of pollutant removal

  5. Designing Experiments that Contr ol for Spatial and Temporal Variation

    Directory of Open Access Journals (Sweden)

    Peter Petraitis

    2003-12-01

    Full Text Available Spatial and temporal variation can cause problems in designing and conducting experiments. An introduction to methods for controlling spatial and temporal variation in ecological experiments is provided in this article. Failure to consider spatial and temporal variation often causes researchers to lay out experiments incorrectly . The challenge is to design experiments that not only reflect the natural variation seen in the field but also control for the variation so that statistical tests have suf ficient power . Spatial variation is usually controlled by grouping observations and treatments into blocks. Blocks can be laid out in a number of ways and Analysis of Variance (ANOV A approaches to control for block effects are discussed. The control of temporal variation presents special dif ficulties because data are often serially correlated and so observations are not independent. Use of intervention analysis and repeated measures analysis of variance to control for temporal variation are discussed. Ecologists have also used experimental designs which are known as BACI designs (i.e., Before-After -Control-Impact design and can be extended to include multiple control and/or impact sites. Intervention analysis, BACI designs, and their extensions have subtle dif ferences because of dif ferent assumptions about not only temporal variation but also spatial variation. Several recommendations are given. These include: 1 the need to have good statistical advice before starting an experiment, 2 the need to have a suf ficient number of replicates that are spread over the range of spatial and temporal variation, and 3 the need to correctly control for serial correlation.

  6. Spatial and temporal variations in residential housing prices in Beijing

    Science.gov (United States)

    Zhang, Yan; Lv, Meng; Yin, Zhongdong

    2009-10-01

    During the past 10 years, the real estate industry in Beijing has been manifesting a strongly growing trend. Researching on the distribution of house prices and their tendencies is helpful to grasp and predict the development of the real estate industry and could be used as reference to city planning. 120 records of housing price data in 2005 to 2006 and open prices in 38 developing projects from the first quarter of 2002 to the second quarter of 2008 were used in this study to analyze the spatial and temporal variations of house price with geostatistical methods and nonlinear regression. Results show that there was a very strong autocorrelation among the house prices in Beijing within the range of about 11 km in 2005 to 2006, which can be well fitted with the spherical model. The isogram of the house prices formed a group of homocentric ellipses, with their long axis extending NW-SE, and the house prices decreased from the center to the periphery. The spatial pattern of house prices in Beijing changed obviously from 2003 to 2006. Although both the spatial patterns for the two periods were homocentric ellipses, the shapes of the ellipses and the directions of the axes changed greatly. And there were more imbalances in 2005 to 2006. The house prices in the Huilongguan-Qinghe residential zone, an example of the typical real estate industry in Beijing, kept growing from 2002 to 2008 and could be fitted with exponential growth model.

  7. Spatial variation in nitrogen dioxide concentrations and cardiopulmonary hospital admissions

    NARCIS (Netherlands)

    Dijkema, Marieke B A; van Strien, Robert T; van der Zee, Saskia C; Mallant, Sanne F; Fischer, Paul; Hoek, Gerard; Brunekreef, Bert; Gehring, Ulrike

    2016-01-01

    BACKGROUND: Air pollution episodes are associated with increased cardiopulmonary hospital admissions. Cohort studies showed associations of spatial variation in traffic-related air pollution with respiratory and cardiovascular mortality. Much less is known in particular about associations with cardi

  8. Building dynamic spatial environmental models

    NARCIS (Netherlands)

    Karssenberg, D.J.

    2003-01-01

    An environmental model is a representation or imitation of complex natural phenomena that can be discerned by human cognitive processes. This thesis deals with the type of environmental models referred to as dynamic spatial environmental models. The word ‘spatial’ refers to the geographic domain whi

  9. Variational approach for spatial point process intensity estimation

    DEFF Research Database (Denmark)

    Coeurjolly, Jean-Francois; Møller, Jesper

    We introduce a new variational estimator for the intensity function of an inhomogeneous spatial point process with points in the d-dimensional Euclidean space and observed within a bounded region. The variational estimator applies in a simple and general setting when the intensity function...... is assumed to be of log-linear form β+θ⊤z(u) where z is a spatial covariate function and the focus is on estimating θ. The variational estimator is very simple to implement and quicker than alternative estimation procedures. We establish its strong consistency and asymptotic normality. We also discuss its...

  10. A neuromorphic model of spatial lookahead planning.

    Science.gov (United States)

    Ivey, Richard; Bullock, Daniel; Grossberg, Stephen

    2011-04-01

    In order to create spatial plans in a complex and changing world, organisms need to rapidly adapt to novel configurations of obstacles that impede simple routes to goal acquisition. Some animals can mentally create successful multistep spatial plans in new visuo-spatial layouts that preclude direct, one-segment routes to goal acquisition. Lookahead multistep plans can, moreover, be fully developed before an animal executes any step in the plan. What neural computations suffice to yield preparatory multistep lookahead plans during spatial cognition of an obstructed two-dimensional scene? To address this question, we introduce a novel neuromorphic system for spatial lookahead planning in which a feasible sequence of actions is prepared before movement begins. The proposed system combines neurobiologically plausible mechanisms of recurrent shunting competitive networks, visuo-spatial diffusion, and inhibition-of-return. These processes iteratively prepare a multistep trajectory to the desired goal state in the presence of obstacles. The planned trajectory can be stored using a primacy gradient in a sequential working memory and enacted by a competitive queuing process. The proposed planning system is compared with prior planning models. Simulation results demonstrate system robustness to environmental variations. Notably, the model copes with many configurations of obstacles that lead other visuo-spatial planning models into selecting undesirable or infeasible routes. Our proposal is inspired by mechanisms of spatial attention and planning in primates. Accordingly, our simulation results are compared with neurophysiological and behavioral findings from relevant studies of spatial lookahead behavior.

  11. Construction of hydrological grid-models based on spatial variation%基于空间变化的栅格水文模型构建

    Institute of Scientific and Technical Information of China (English)

    王秀云; 王贵作; 王斌; 王海涛; 徐振文

    2011-01-01

    传统水文模型在水量模拟实践中取得了一些满意的结果,但由于传统水文模型大多不能反映下垫面特性对降雨径流过程的影响,从而限制了其在更广泛涉水领域的应用和发展.本文在地貌形成理论的基础上,充分考虑了流域内地形、植被、土壤、土壤水分参数等因素对流域蓄水容量空间分布的影响,提出了基于栅格蓄水容量空间变异的分布式水文模型.%Traditional hydrological models were robust in water quantity simulation. However,these models were very weak in calculating the impact of the underlying surface on the rainfall-runoff process, and this drawback limited the application and development of traditional models. On the basis of geomorphic process theory, it took into account several hydrological related factors such as watershed terrain, vegetation cover, soil type and soil moisture parameters, meanwhile these factors' impact on the spatial distribution of watershed water storage capacity. It brought out a spatial distributed model of water storage capacity, and integrated it with the saturation excess runoff mechanism and the vertically-mixed runoff mechanism into watershed hydrologic models based on the spatial distributed model of water storage capacity. This model structure was reasonable relatively, and was used to the study process simulation, discipline of evapotranspiration pattern, and watershed drought assessment and classification.

  12. A physically based analytical spatial air temperature and humidity model

    Science.gov (United States)

    Yang Yang; Theodore A. Endreny; David J. Nowak

    2013-01-01

    Spatial variation of urban surface air temperature and humidity influences human thermal comfort, the settling rate of atmospheric pollutants, and plant physiology and growth. Given the lack of observations, we developed a Physically based Analytical Spatial Air Temperature and Humidity (PASATH) model. The PASATH model calculates spatial solar radiation and heat...

  13. Latent spatial models and sampling design for landscape genetics

    Science.gov (United States)

    Hanks, Ephraim M.; Hooten, Mevin B.; Knick, Steven T.; Oyler-McCance, Sara J.; Fike, Jennifer A.; Cross, Todd B.; Schwartz, Michael K.

    2016-01-01

    We propose a spatially-explicit approach for modeling genetic variation across space and illustrate how this approach can be used to optimize spatial prediction and sampling design for landscape genetic data. We propose a multinomial data model for categorical microsatellite allele data commonly used in landscape genetic studies, and introduce a latent spatial random effect to allow for spatial correlation between genetic observations. We illustrate how modern dimension reduction approaches to spatial statistics can allow for efficient computation in landscape genetic statistical models covering large spatial domains. We apply our approach to propose a retrospective spatial sampling design for greater sage-grouse (Centrocercus urophasianus) population genetics in the western United States.

  14. Modelling of human low frequency sound localization acuity demonstrates dominance of spatial variation of interaural time difference and suggests uniform just-noticeable differences in interaural time difference.

    Directory of Open Access Journals (Sweden)

    Rosanna C G Smith

    Full Text Available Sound source localization is critical to animal survival and for identification of auditory objects. We investigated the acuity with which humans localize low frequency, pure tone sounds using timing differences between the ears. These small differences in time, known as interaural time differences or ITDs, are identified in a manner that allows localization acuity of around 1° at the midline. Acuity, a relative measure of localization ability, displays a non-linear variation as sound sources are positioned more laterally. All species studied localize sounds best at the midline and progressively worse as the sound is located out towards the side. To understand why sound localization displays this variation with azimuthal angle, we took a first-principles, systemic, analytical approach to model localization acuity. We calculated how ITDs vary with sound frequency, head size and sound source location for humans. This allowed us to model ITD variation for previously published experimental acuity data and determine the distribution of just-noticeable differences in ITD. Our results suggest that the best-fit model is one whereby just-noticeable differences in ITDs are identified with uniform or close to uniform sensitivity across the physiological range. We discuss how our results have several implications for neural ITD processing in different species as well as development of the auditory system.

  15. Spatial variation of the longitudinal dispersion coefficient in an estuary

    OpenAIRE

    D. C. Shaha; Y.-K. Cho; M.-T. Kwak; S. R. Kundu; K. T. Jung

    2011-01-01

    The effective longitudinal dispersion is a primary tool for determining property distributions in estuaries. Most previous studies have examined the longitudinal dispersion coefficient for the average tidal condition. However, information on spatial and temporal variations of this coefficient at low and high tide is scarce. Three years of hydrographic data taken at low and high tide along the main axis of the Sumjin River Estuary (SRE), Korea are used to estimate the spatial and temporal vari...

  16. Thermodynamic Model of Spatial Memory

    Science.gov (United States)

    Kaufman, Miron; Allen, P.

    1998-03-01

    We develop and test a thermodynamic model of spatial memory. Our model is an application of statistical thermodynamics to cognitive science. It is related to applications of the statistical mechanics framework in parallel distributed processes research. Our macroscopic model allows us to evaluate an entropy associated with spatial memory tasks. We find that older adults exhibit higher levels of entropy than younger adults. Thurstone's Law of Categorical Judgment, according to which the discriminal processes along the psychological continuum produced by presentations of a single stimulus are normally distributed, is explained by using a Hooke spring model of spatial memory. We have also analyzed a nonlinear modification of the ideal spring model of spatial memory. This work is supported by NIH/NIA grant AG09282-06.

  17. Spatial variation of reference crop evapotranspiration on Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    Yong-hong YANG; Zhan-yu ZHANG; Xin-yi XIANG

    2009-01-01

    This study is based on meteorological observation data collected at 38 weather stations on the Tibetan Plateau over several decades. Daily reference crop evapotranspiration (ET0) was calculated with the FAO-56 standard Penman-Monteith formula. A test of normality was performed with Statistica 6.0 software, isotropic and anisotropic semi-variogram analysis was conducted with the GS+ (geostatistics for the environmental sciences) system for Windows 7.0, and the characteristics of spatial variation of daily ET0 were obtained. The following results can be obtained: Daily ETo for different periods on the Tibetan Plateau are distributed normally; Except for daily ETo in the E-W (east-west) direction in the summer, which showed a slight negative correlation with distance change, the Moran's indexes of daily ET0 for different periods in all directions on the Tibetan Plateau within a 100-km distance were positive, demonstrating a positive correlation with distance change; Variograms of daily ET0 in June, the dry season, the wet season, as well as annual average daily ET0 fit well with the Gaussian model; A variogram of daily ET0 in December fit well with the exponential model; Variograms of daily ET0 for the four seasons fit well with the linear with sill model.

  18. Spatial variation of vulnerability in geographic areas of North Lebanon

    NARCIS (Netherlands)

    Issa, Sahar; van der Molen, Peterdina; Nader, M.R.; Lovett, Jonathan Cranidge

    2014-01-01

    This paper examines the spatial variation in vulnerability between different geographical areas of the northern coastal region of Lebanon within the context of armed conflict. The study is based on the ‘vulnerability of space’ approach and will be positioned in the academic debate on vulnerability

  19. Temporal and spatial variations in fly ash quality

    Science.gov (United States)

    Hower, J.C.; Trimble, A.S.; Eble, C.F.

    2001-01-01

    Fly ash quality, both as the amount of petrographically distinguishable carbons and in chemistry, varies in both time and space. Temporal variations are a function of a number of variables. Variables can include variations in the coal blend organic petrography, mineralogy, and chemistry; variations in the pulverization of the coal, both as a function of the coal's Hardgrove grindability index and as a function of the maintenance and settings of the pulverizers; and variations in the operating conditions of the boiler, including changes in the pollution control system. Spatial variation, as an instantaneous measure of fly ash characteristics, should not involve changes in the first two sets of variables listed above. Spatial variations are a function of the gas flow within the boiler and ducts, certain flow conditions leading to a tendency for segregation of the less-dense carbons in one portion of the gas stream. Caution must be applied in sampling fly ash. Samples from a single bin, or series of bins, m ay not be representative of the whole fly ash, providing a biased view of the nature of the material. Further, it is generally not possible to be certain about variation until the analysis of the ash is complete. ?? 2001 Elsevier Science B.V. All rights reserved.

  20. Modeling for spatial multilevel structural data

    Science.gov (United States)

    Min, Suqin; He, Xiaoqun

    2013-03-01

    The traditional multilevel model assumed independence between groups. However, the datasets grouped by geographical units often has spatial dependence. The individual is influenced not only by its region but also by the adjacent regions, and level-2 residual distribution assumption of traditional multilevel model is violated. In order to deal with such spatial multilevel data, we introduce spatial statistics and spatial econometric models into multilevel model, and apply spatial parameters and adjacency matrix in traditional level-2 model to reflect the spatial autocorrelation. Spatial lag model express spatial effects. We build spatial multilevel model which consider both multilevel thinking and spatial correlation.

  1. A Digital Model to Simulate Effects of Bone Architecture Variations on Texture at Spatial Resolutions of CT, HR-pQCT, and μCT Scanners

    Directory of Open Access Journals (Sweden)

    T. Lowitz

    2014-01-01

    Full Text Available The quantification of changes in the trabecular bone structure induced by musculoskeletal diseases like osteoarthritis, osteoporosis, rheumatoid arthritis, and others by means of a texture analysis is a valuable tool which is expected to improve the diagnosis and monitoring of a disease. The reaction of texture parameters on different alterations in the architecture of the fine trabecular network and inherent imaging factors such as spatial resolution or image noise has to be understood in detail to ensure an accurate and reliable determination of the current bone state. Therefore, a digital model for the quantitative analysis of cancellous bone structures was developed. Five parameters were used for texture analysis: entropy, global and local inhomogeneity, local anisotropy, and variogram slope. Various generic structural changes of cancellous bone were simulated for different spatial resolutions. Additionally, the dependence of the texture parameters on tissue mineralization and noise was investigated. The present work explains changes in texture parameter outcomes based on structural changes originating from structure modifications and reveals that a texture analysis could provide useful information for a trabecular bone analysis even at resolutions below the dimensions of single trabeculae.

  2. Modeling of pulsed K DPAL taking into account the spatial variation of the pump and laser intensities in the transverse direction

    Science.gov (United States)

    Barmashenko, Boris D.; Auslender, Ilya; Rosenwaks, Salman; Zhdanov, Boris; Rotondaro, Matthew; Knize, Randall J.

    2015-10-01

    We report on a model of highly efficient static, pulsed K DPAL [Zhdanov et al, Optics Express 22, 17266 (2014)], where Gaussian spatial shapes of the pump and laser intensities in any cross section of the beams are assumed. The model shows good agreement between the calculated and measured dependence of the laser power on the incident pump power. In particular, the model reproduces the observed threshold pump power, 22 W (corresponding to pump intensity of 4 kW/cm2), which is much higher than that predicted by the standard semi-analytical models of the DPAL. The reason for the large values of the threshold power is that the volume occupied by the excited K atoms contributing to the spontaneous emission is much larger than the volumes of the pump and laser beams in the laser cell, resulting in very large energy losses due to the spontaneous emission. To reduce the adverse effect of the high threshold power, high pump power is needed, and therefore gas flow with high gas velocity to avoid heating the gas has to be applied. Thus, for obtaining high power, highly efficient K DPAL, subsonic or supersonic flowing-gas device is needed.

  3. Spatial and temporal variations of aridity indices in Iraq

    Science.gov (United States)

    Şarlak, Nermin; Mahmood Agha, Omar M. A.

    2017-06-01

    This study investigates the spatial and temporal variations of the aridity indices to reveal the desertification vulnerability of Iraq region. Relying on temperature and precipitation data taken from 28 meteorological stations for 31 years, the study aims to determine (1) dry land types and their delineating boundaries and (2) temporal change in aridity conditions in Iraq. Lang's aridity (Im), De Martonne's aridity (Am), United Nations Environmental Program (UNEP) aridity (AIu), and Erinç aridity (IE) indices were selected in this study because of the scarcity of the observed data. The analysis of the spatial variation of aridity indices exhibited that the arid and semi-arid regions cover about 97% of the country's areas. As for temporal variations, it was observed that the aridity indices tend to decrease (statistically significant or not) for all stations. The cumulative sum charts (CUSUMs) were applied to detect the year on which the climate pattern of aridity indices had changed from one pattern to another. The abrupt change point was detected around year 1997 for the majority of the stations. Thus, the spatial and temporal aridity characteristics in Iraq were examined for the two periods 1980-1997 and 1998-2011 (before and after the change-point year) to observe the influence of abrupt change point on aridity phenomena. The spatial variation after 1997 was observed from semi-arid (dry sub humid) to arid (semi-arid) especially at the stations located in northern Iraq, while hyper-arid and arid climatic conditions were still dominant over southern and central Iraq. Besides, the negative temporal variations of the two periods 1980-1997 and 1998-2011 were obtained for almost every station. As a result, it was emphasized that Iraq region, like other Middle East regions, has become drier after 1997. The observed reduction in precipitation and increase in temperature for this region seem to make the situation worse in future.

  4. Spatial and seasonal variations of polycyclic aromatic hydrocarbons in Haihe Plain, China

    Energy Technology Data Exchange (ETDEWEB)

    Wang Rong [Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871 (China); Cao Hongying, E-mail: caohy@igsnrr.ac.cn [Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101 (China); Li Wei; Wang Wei; Wang Wentao; Zhang Liwen; Liu Jiumeng; Ouyang Huiling; Tao Shu [Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871 (China)

    2011-05-15

    A dynamic fugacity model was developed to simulate the spatial and seasonal variations of PAHs in Haihe Plain, China. The calculated and measured concentrations exhibited good consistency in magnitude with deviations within a factor of 4 in air and 2 in soil. The spatial distributions of PAHs in air were mainly controlled by emission while the seasonal variations were dominated by emission and gas-particle partition. In soil, the spatial distributions of PAHs were controlled by the soil organic carbon content while the seasonal variations were insignificant. The severest soil contamination was observed in Shanxi and followed by the southwest of Hebei province. Transfer fluxes of total PAHs between air and soil were calculated. The spatial distribution of air-to-soil flux was closely related to the landcover while the soil-to-air flux changed with soil organic matter content. Monte Carlo simulation was done to evaluate the uncertainty of the estimated results in air. - Highlights: > A Level IV dynamic model with spatial resolution was developed. > The model was applied to address the fate of PAHs in Haihe Plain, China. > The severest soil contamination was observed in Shanxi and followed by the southwest of Hebei province. > The air-to-soil flux was closely related to the landcover while the soil-to-air flux changed with soil organic matter content. > The model results proved to have less uncertainty than regular level IV model without spatial resolution. - Spatial and seasonal variations of PAHs in Haihe Plain were studied using a dynamic fugacity model with spatial resolution.

  5. Spatial Variation of the Correlated Color Temperature of Lightning Channel

    CERN Document Server

    Shimoji, Nobuaki; Sakihama, Singo

    2014-01-01

    In this paper, we studied the spatial variation of the correlated color temperature (CCT) of lightning channel. We also discussed the energy of lightning channels relating to the CCT . First we applied digital image processing techniques to lightning images. In order to reduce the chromatic aberration, we created the reduction technique algorithm of the chromatic aberration on digital still images. We applied the reduction technique of the chromatic aberration to digital still images, and then the obtained results was mapped to the xy-chromaticity diagram. The CCT of the lightning channel was decided on the xy-chromaticity diagram. From results, the spatial variation of the CCT of the lightning channel was confirmed. Then the energy associated with the the CCT was discussed.

  6. Spatial Variation of Arsenic in Soil, Irrigation Water, and Plant Parts: A Microlevel Study

    OpenAIRE

    Kabir, M. S.; Salam, M.A.; Paul, D. N. R.; Hossain, M. I.; Rahman, N.M.F; Abdullah Aziz; Latif, M.A.

    2016-01-01

    Arsenic pollution became a great problem in the recent past in different countries including Bangladesh. The microlevel studies were conducted to see the spatial variation of arsenic in soils and plant parts contaminated through ground water irrigation. The study was performed in shallow tube well command areas in Sadar Upazila (subdistrict), Faridpur, Bangladesh, where both soil and irrigation water arsenic are high. Semivariogram models were computed to determine the spatial dependency of s...

  7. Competition in spatial location models

    NARCIS (Netherlands)

    Webers, H.M.

    1996-01-01

    Models of spatial competition are designed and analyzed to describe the fact that space, by its very nature, is a source of market power. This field of research, lying at the interface of game theory and economics, has attracted much interest because location problems are related to many aspects of

  8. Competition in spatial location models

    NARCIS (Netherlands)

    Webers, H.M.

    1996-01-01

    Models of spatial competition are designed and analyzed to describe the fact that space, by its very nature, is a source of market power. This field of research, lying at the interface of game theory and economics, has attracted much interest because location problems are related to many aspects of

  9. Spatial and temporal variations in nitrogen sources and cycling in north San Francisco Bay: Combining multi-isotope and hydrologic modeling approaches

    Science.gov (United States)

    Young, M. B.; Kendall, C.; Silva, S. R.; Guerin, M.; Kraus, T. E.

    2010-12-01

    In order to better understand the factors controlling nitrogen sources and cycling within Suisun Bay and the Sacramento-San Joaquin River confluence, stable isotope measurements of nitrate (NO3), water, and particulate organic matter (POM) were combined with estimates of volumetric water source contributions calculated using the DSM2-HYDRO hydrodynamic model. The San Joaquin River (SJR) typically carries high concentrations of NO3, while the Sacramento River downstream of the Sacramento Regional Waste Water Treatment Plant (SRWWTP) has high concentrations of ammonium (NH4). Samples were collected at established USGS stations from the lower Sacramento River and north San Francisco Bay on 16 occasions between August 2006 and May 2008, and along transects of the SJR between March 2005 and December 2007. The average δ15N of NO3 discharging from the SJR was consistently higher (13.0 ± 2.1 ‰, upstream of pumping diversion) in comparison to the Sacramento River (5.3 ± 0.9 ‰, sampled at Rio Vista), indicating that δ15N-NO3 can be useful for tracking NO3 from the two watersheds as it mixes in the confluence region. Results from the DSM2-HYDRO model show that during the study period the SJR contributed very little water (less than 1.5 %) to sites located at the Sacramento/SJR confluence and downstream in Suisun Bay. The distribution of δ15N-NO3 values in the confluence area and north Bay was consistent with this result, showing a fairly narrow range of lower values (3.5 to 9.5 ‰), indicating that little to no NO3 from the SJR watershed was reaching the confluence area and the north Bay during the sampling times. In the SJR, the C:N ratio of POM was usually between 6 and 10 except during periods of high winter flows, indicating that the POM was primarily algae most of the year. The δ15N of POM within the SJR was generally between 2 and 4 per mil lower than the δ15N of the NO3 and followed a similar pattern to the NO3, reflecting algal uptake of the NO3. In

  10. Variational methods in molecular modeling

    CERN Document Server

    2017-01-01

    This book presents tutorial overviews for many applications of variational methods to molecular modeling. Topics discussed include the Gibbs-Bogoliubov-Feynman variational principle, square-gradient models, classical density functional theories, self-consistent-field theories, phase-field methods, Ginzburg-Landau and Helfrich-type phenomenological models, dynamical density functional theory, and variational Monte Carlo methods. Illustrative examples are given to facilitate understanding of the basic concepts and quantitative prediction of the properties and rich behavior of diverse many-body systems ranging from inhomogeneous fluids, electrolytes and ionic liquids in micropores, colloidal dispersions, liquid crystals, polymer blends, lipid membranes, microemulsions, magnetic materials and high-temperature superconductors. All chapters are written by leading experts in the field and illustrated with tutorial examples for their practical applications to specific subjects. With emphasis placed on physical unders...

  11. Meteorology-induced variations in the spatial behavior of summer ozone pollution in Central California

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Ling; Harley, Robert A.; Brown, Nancy J.

    2010-06-23

    Cluster analysis was applied to daily 8 h ozone maxima modeled for a summer season to characterize meteorology-induced variations in the spatial distribution of ozone. Principal component analysis is employed to form a reduced dimension set to describe and interpret ozone spatial patterns. The first three principal components (PCs) capture {approx}85% of total variance, with PC1 describing a general spatial trend, and PC2 and PC3 each describing a spatial contrast. Six clusters were identified for California's San Joaquin Valley (SJV) with two low, three moderate, and one high-ozone cluster. The moderate ozone clusters are distinguished by elevated ozone levels in different parts of the valley: northern, western, and eastern, respectively. The SJV ozone clusters have stronger coupling with the San Francisco Bay area (SFB) than with the Sacramento Valley (SV). Variations in ozone spatial distributions induced by anthropogenic emission changes are small relative to the overall variations in ozone amomalies observed for the whole summer. Ozone regimes identified here are mostly determined by the direct and indirect meteorological effects. Existing measurement sites are sufficiently representative to capture ozone spatial patterns in the SFB and SV, but the western side of the SJV is under-sampled.

  12. Role of spatial variability of rainfall intensity: improve- ment of Eagleson's classical model to explain the rela- tionship between the coefficient of variation of annual maximum discharge and catchment size

    Science.gov (United States)

    Kuzuha, Yasuhisa; Sivapalan, Murugesu; Tomosugi, Kunio; Kishii, Tokuo; Komatsu, Yosuke

    2006-04-01

    Eagleson's classical regional flood frequency model is investigated. Our intention was not to improve the model, but to reveal previously unidentified important and dominant hydrological processes in it. The change of the coefficient of variation (CV) of annual maximum discharge with catchment area can be viewed as representing the spatial variance of floods in a homogeneous region. Several researchers have reported that the CV decreases as the catchment area increases, at least for large areas. On the other hand, Eagleson's classical studies have been known as pioneer efforts that combine the concept of similarity analysis (scaling) with the derived flood frequency approach. As we have shown, the classical model can reproduce the empirical relationship between the mean annual maximum discharge and catchment area, but it cannot reproduce the empirical decreasing CV-catchment area curve. Therefore, we postulate that previously unidentified hydrological processes would be revealed if the classical model were improved to reproduce the decreasing of CV with catchment area. First, we attempted to improve the classical model by introducing a channel network, but this was ineffective. However, the classical model was improved by introducing a two-parameter gamma distribution for rainfall intensity. What is important is not the gamma distribution itself, but those characteristics of spatial variability of rainfall intensity whose CV decreases with increasing catchment area. Introducing the variability of rainfall intensity into the hydrological simulations explains how the CV of rainfall intensity decreases with increasing catchment area. It is difficult to reflect the rainfall-runoff processes in the model while neglecting the characteristics of rainfall intensity from the viewpoint of annual flood discharge variances.

  13. Variational denoising of partly textured images by spatially varying constraints.

    Science.gov (United States)

    Gilboa, Guy; Sochen, Nir; Zeevi, Yehoshua Y

    2006-08-01

    Denoising algorithms based on gradient dependent regularizers, such as nonlinear diffusion processes and total variation denoising, modify images towards piecewise constant functions. Although edge sharpness and location is well preserved, important information, encoded in image features like textures or certain details, is often compromised in the process of denoising. We propose a mechanism that better preserves fine scale features in such denoising processes. A basic pyramidal structure-texture decomposition of images is presented and analyzed. A first level of this pyramid is used to isolate the noise and the relevant texture components in order to compute spatially varying constraints based on local variance measures. A variational formulation with a spatially varying fidelity term controls the extent of denoising over image regions. Our results show visual improvement as well as an increase in the signal-to-noise ratio over scalar fidelity term processes. This type of processing can be used for a variety of tasks in partial differential equation-based image processing and computer vision, and is stable and meaningful from a mathematical viewpoint.

  14. Spatial Variation of Temperature and Precipitation in Bhutan and Links to Vegetation and Land Cover

    Directory of Open Access Journals (Sweden)

    Ugyen Dorji

    2016-02-01

    Full Text Available Bhutan, located in the Himalayas in the South Asian monsoon region, has extremely high variation in elevation, climatic conditions, and land cover despite its small geographical area, as well as great biodiversity. This paper provides the first comprehensive description of climatic conditions in Bhutan. It assesses the spatial variation of temperature and precipitation across the country and evaluates the causes for this variation based on daily data from 70 meteorological stations that have been recording data for time spans ranging from 3 to 21 years. Temperature and precipitation show contrasting spatial variation, with temperature primarily affected by elevation and precipitation by latitude. Models were developed using mixed linear regression models to predict seasonal and annual mean temperature and precipitation based on geographical location. Using linear regression we found that temperatures changed by about 0.5°C for every 100 m of change in elevation, with lapse rates being highest in February, March, and November and lowest from June to August. The lapse rate was highest for minimum temperatures and lowest for maximum temperatures, with the greatest difference during winter. The spatial distribution of precipitation was mainly controlled by latitude, having a quadratic relationship, with the highest rates in the southern foothills of the Himalayan range and the lowest at midlatitudes. The land cover is affected by topography and local climate, with variations in temperature being a main deciding factor for vegetation types; most human settlements and associated land uses are concentrated at lower elevations.

  15. An analysis on spatial variation of urban human thermal comfort in Hangzhou,China

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-wu; ZHU Li-zhong; WANG Ren-chao

    2004-01-01

    Urban human thermal comfort (UHTC) is affected for interacting of weather condition and underlyingsurface framework of urban area. Urban underlying surface temperature value and Normalized Difference VegetationIndex(NDVI) were calculated using image interpreting and supervised classification technique by ERDAS IMAGEsoftware using 1991 and 1999 Landsat TM images data. Reference to the relational standard of assessing humanthermal comfort and other meteorology data of Hangzhou City in summer, air temperature and relative humidityvariation of different land types of underlying surface were inversed. By choosing discomfort index as an indictor, thespatial distribution characteristic and the spatial variation degree of UHTC were estimated and mapped on a middlescale, that is, in six districts of Hangzhou. The main characteristics of UHTC spatial variation from 1991 to 1999 wererevealed using a GIS-based calculation model. The variation mechanism were analyzed and discussed from theviewpoint of city planning, construction and environmental protection.

  16. Variational Methods for Biomolecular Modeling

    CERN Document Server

    Wei, Guo-Wei

    2016-01-01

    Structure, function and dynamics of many biomolecular systems can be characterized by the energetic variational principle and the corresponding systems of partial differential equations (PDEs). This principle allows us to focus on the identification of essential energetic components, the optimal parametrization of energies, and the efficient computational implementation of energy variation or minimization. Given the fact that complex biomolecular systems are structurally non-uniform and their interactions occur through contact interfaces, their free energies are associated with various interfaces as well, such as solute-solvent interface, molecular binding interface, lipid domain interface, and membrane surfaces. This fact motivates the inclusion of interface geometry, particular its curvatures, to the parametrization of free energies. Applications of such interface geometry based energetic variational principles are illustrated through three concrete topics: the multiscale modeling of biomolecular electrosta...

  17. Spatial variation and prediction of forest biomass in a heterogeneous landscape

    Institute of Scientific and Technical Information of China (English)

    S.Lamsal; D.M.Rizzo; R.K.Meentemeyer

    2012-01-01

    Large areas assessments of forest biomass distribution are a challenge in heterogeneous landscapes,where variations in tree growth and species composition occur over short distances.In this study,we use statistical and geospatial modeling on densely sampled forest biomass data to analyze the relative importance of ecological and physiographic variables as determinants of spatial variation of forest biomass in the environmentally heterogeneous region of the Big Sur,California.We estimated biomass in 280 forest plots (one plot per 2.85 km2) and measured an array of ecological (vegetation community type,distance to edge,amount of surrounding non-forest vegetation,soil properties,fire history) and physiographic drivers (elevation,potential soil moisture and solar radiation,proximity to the coast) of tree growth at each plot location.Our geostatistical analyses revealed that biomass distribution is spatially structured and autocorrelated up to 3.1 km.Regression tree (RT) models showed that both physiographic and ecological factors influenced biomass distribution.Across randomly selected sample densities (sample size 112 to 280),ecological effects of vegetation community type and distance to forest edge,and physiographic effects of elevation,potentialsoil moisture and solar radiation were the most consistent predictors of biomass.Topographic moisture index and potential solar radiation had a positive effect on biomass,indicating the importance of topographicallymediated energy and moisture on plant growth and biomass accumulation.RT model explained 35% of the variation in biomass and spatially autocorrelated variation were retained in regession residuals.Regression kriging model,developed from RT combined with kriging of regression residuals,was used to map biomass across the Big Sur.This study demonstrates how statistical and geospatial modeling can be used to discriminate the relative importance of physiographic and ecologic effects on forest biomass and develop

  18. Numerical studies on spatial variation of the in situ stress field at Forsmark - a further step. Site descriptive modelling Forsmark - stage 2.1

    Energy Technology Data Exchange (ETDEWEB)

    Hakami, Hossein [Itasca Geomekanik AB, Solna (Sweden)

    2006-12-15

    The present work is an investigation into the depiction of a spatial distribution of the in situ stresses at the Forsmark candidate site. The methodology is based on numerical simulations of the pre-occurrences of perturbation of the stress field, produced by the deformations/displacements that rock mass/major fracture zones undergo. The distinct element program DEC, was used for the purpose. Forsmark area is dominated mainly by the Forsmark and the Singoe faults but also by a number of major fracture zones. Almost all these structures, not only that they are reported to dip vertically, but they more or less run sub-parallel with the inferred overall orientation of the major principal stress, s1. These zones, as a result, cause a fairly limited perturbation in the state of in situ stress at the site. At a diminished scale, however, fracture zones of a lesser extent - which dip obliquely and run at an angle in relation to the s1 orientation - produce a significant perturbation of the state of stress. This work also included two preliminary investigations on: - Assessing the remote orientation of the major principal stress. This was done by looking at the crustal shortening, which characterizes in part the past tectonic activities of the Fennoscandian shield. - Looking for the mechanically viable explanations for the formation of joints sub-parallel with ground surface within the uppermost section of the rock mass.

  19. Emergence of Strange Spatial Pattern in a Spatial Epidemic Model

    Institute of Scientific and Technical Information of China (English)

    SUN Gui-Quan; JIN Zhen; LIU Quan-Xing; LI Li

    2008-01-01

    Pattern formation of a spatial epidemic model with nonlinear incidence rate kI2 S/ (1 + αI2) is investigated. Our results show that strange spatial dynamics, i.e., filament-like pattern, can be obtained by both mathematical analysis and numerical simulation, which are different from the previous results in the spatial epidemic model such as stripe-like or spotted or coexistence of both pattern and so on. The obtained results well extend the finding of pattern formation in the epidemic model and may well explain the distribution of the infected of some epidemic.

  20. Recovery Act: An Integrated Experimental and Numerical Study: Developing a Reaction Transport Model that Couples Chemical Reactions of Mineral Dissolution/Precipitation with Spatial and Temporal Flow Variations.

    Energy Technology Data Exchange (ETDEWEB)

    Saar, Martin O. [ETH Zurich (Switzerland); Univ. of Minnesota, Minneapolis, MN (United States); Seyfried, Jr., William E. [Univ. of Minnesota, Minneapolis, MN (United States); Longmire, Ellen K. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-06-24

    A total of 12 publications and 23 abstracts were produced as a result of this study. In particular, the compilation of a thermodynamic database utilizing consistent, current thermodynamic data is a major step toward accurately modeling multi-phase fluid interactions with solids. Existing databases designed for aqueous fluids did not mesh well with existing solid phase databases. Addition of a second liquid phase (CO2) magnifies the inconsistencies between aqueous and solid thermodynamic databases. Overall, the combination of high temperature and pressure lab studies (task 1), using a purpose built apparatus, and solid characterization (task 2), using XRCT and more developed technologies, allowed observation of dissolution and precipitation processes under CO2 reservoir conditions. These observations were combined with results from PIV experiments on multi-phase fluids (task 3) in typical flow path geometries. The results of the tasks 1, 2, and 3 were compiled and integrated into numerical models utilizing Lattice-Boltzmann simulations (task 4) to realistically model the physical processes and were ultimately folded into TOUGH2 code for reservoir scale modeling (task 5). Compilation of the thermodynamic database assisted comparisons to PIV experiments (Task 3) and greatly improved Lattice Boltzmann (Task 4) and TOUGH2 simulations (Task 5). PIV (Task 3) and experimental apparatus (Task 1) have identified problem areas in TOUGHREACT code. Additional lab experiments and coding work has been integrated into an improved numerical modeling code.

  1. Orbital effects of spatial variations of fundamental coupling constants

    CERN Document Server

    Iorio, Lorenzo

    2011-01-01

    We deal with the effects induced on the orbit of a test particle revolving around a central body by putative spatial variations of fundamental coupling constants $\\zeta$. In particular, we assume a dipole gradient for $\\zeta(\\bds r)/\\bar{\\zeta}$ along a generic direction $\\bds{\\hat{k}}$ in space. We analytically work out the long-term variations of all the six standard Keplerian orbital elements parameterizing the orbit of a test particle in a gravitationally bound two-body system. It turns out that, apart from the semi-major axis $a$, the eccentricity $e$, the inclination $I$, the longitude of the ascending node $\\Omega$, the longitude of pericenter $\\pi$ and the mean anomaly $\\mathcal{M}$ undergo non-zero long-term changes. By using the usual decomposition along the radial ($R$), transverse ($T$) and normal ($N$) directions, we also analytically work out the long-term changes $\\Delta R,\\Delta T,\\Delta N$ and $\\Delta v_R,\\Delta v_T,\\Delta v_N$ experienced by the position and the velocity vectors $\\bds r$ and...

  2. Identifying spatial and temporal variations in seismicity in eastern Canada

    Science.gov (United States)

    Tiampo, K. F.; Atkinson, G. M.; Fereidoni, A.; Bhattacharya, P.; Cho, N.; Kazemian, J.; Vincent, P.; Gonzalez, P. J.

    2012-12-01

    Natural earthquake fault systems are highly heterogeneous in space; inhomogeneities occur because of the varying internal structures and material strengths that dissipate stress differently. However, because analysis of the actual earthquake fault system remains incomplete due to the inherent difficulty in sampling the solid Earth (Richter, 1958; Kanamori, 1981; Geller et al., 1997), much of the recent research in statistical seismology has centered on investigating the variety of spatial and temporal patterns that exist in local and regional data. In particular, in recent years a combination of theoretical analysis, numerical simulations and seismicity data analysis has established the link between variations in seismicity rates and the dynamics of the underlying stress field (Dieterich, 1994; Dieterich et al., 2002; Toda et al., 2002; Rundle et al., 2002; Tiampo et al., 2002, 2006; Schorlemmer and Wiemer, 2005). However, this research has predominantly focused on tectonically-active regions with a relatively high rate of background seismicity. Here we present new work that quantifies seismicity rate changes in the intraplate region of eastern Canada in order to identify spatial and temporal variations in local and regional stress (Tiampo et al, 2002, 2006). Although stable eastern North America generally has much lower seismicity than plate boundary regions, there are areas of substantial seismicity and earthquake hazard. The bulk of the eastern Canadian seismicity is concentrated in both the lower Saint Lawrence seismic zone, downriver from Québec City and the Charlevoix seismic zone to the west of Québec City. Although Mazzotti and Adams (2005) estimate that seismic strain rates in most of eastern Canada are about 10-13 to 10-11/yr, exceptions to these low strain rates can be found in these regions of higher seismic activation. These seismically active zones generally are associated with large lithospheric-scale paleotectonic geologic features and this strong

  3. Glacial cycles and solar insolation: the role of orbital, seasonal, and spatial variations

    Science.gov (United States)

    Kaufmann, R. K.; Juselius, K.

    2010-11-01

    We use a statistical model, the cointegrated vector autoregressive model, to evaluate the relative roles that orbital, seasonal, and spatial variations in solar insolation play in glacial cycles during the late Quaternary (390kyr - present). To do so, we estimate models of varying complexity and compare the accuracy of their in-sample simulations. Results indicate that variations in solar insolation associated with changes in Earth's orbit have the greatest explanatory power and that obliquity, precession, and eccentricity are needed to generate an accurate simulation of glacial cycles. Seasonal variations in insolation play a lesser role, while cumulative summer-time insolation has little explanatory power. Finally, solar insolation in the Northern Hemisphere generates the more accurate in-sample simulation of surface temperature while ice volume is simulated most accurately by solar insolation in the Southern Hemisphere.

  4. Topography induced spatial variations in diurnal cycles of assimilation and latent heat of Mediterranean forest

    Directory of Open Access Journals (Sweden)

    C. van der Tol

    2007-01-01

    Full Text Available The aim of this study is to explain topography induced spatial variations in the diurnal cycles of assimilation and latent heat of Mediterranean forest. Spatial variations of the fluxes are caused by variations in weather conditions and in vegetation characteristics. Weather conditions reflect short-term effects of climate, whereas vegetation characteristics, through adaptation and acclimation, long-term effects of climate. In this study measurements of plant physiology and weather conditions are used to explain observed differences in the fluxes. A model is used to study which part of the differences in the fluxes is caused by weather conditions and which part by vegetation characteristics. Data were collected at four experimental sub-Mediterranean deciduous forest plots in a heterogeneous terrain with contrasting aspect, soil water availability, humidity and temperature. We used a sun-shade model to scale fluxes from leaf to canopy, and calculated the canopy energy balance. Parameter values were derived from measurements of light interception, leaf chamber photosynthesis, leaf nitrogen content and 13C isotope discrimination in leaf material. Leaf nitrogen content is a measure of photosynthetic capacity, and 13C isotope discrimination of water use efficiency. For validation, sap-flux based measurements of transpiration were used. The model predicted diurnal cycles of transpiration and stomatal conductance, both their magnitudes and differences in afternoon stomatal closure between slopes of different aspect within the confidence interval of the validation data. Weather conditions mainly responsible for the shape of the diurnal cycles, and vegetation parameters for the magnitude of the fluxes. Although the data do not allow for a quantification of the two effects, the differences in vegetation parameters and weather among the plots and the sensitivity of the fluxes to them suggest that the diurnal cycles were more strongly affected by spatial

  5. Fine-scale spatial variation in plant species richness and its relationship to environmental conditions in coastal marshlands

    Science.gov (United States)

    Mancera, J.E.; Meche, G.C.; Cardona-Olarte, P.P.; Castaneda-Moya, E.; Chiasson, R.L.; Geddes, N.A.; Schile, L.M.; Wang, H.G.; Guntenspergen, G.R.; Grace, J.B.

    2005-01-01

    Previous studies have shown that variations in environmental conditions play a major role in explaining variations in plant species richness at community and landscape scales. In this study, we considered the degree to which fine-scale spatial variations in richness could be related to fine-scale variations in abiotic and biotic factors. To examine spatial variation in richness, grids of 1 m(2) plots were laid out at five sites within a coastal riverine wetland landscape. At each site, a 5 x 7 array of plots was established adjacent to the river's edge with plots one meter apart. In addition to the estimation of species richness, environmental measurements included sediment salinity, plot microelevation, percent of plot recently disturbed, and estimated community biomass. Our analysis strategy was to combine the use of structural equation modeling (path modeling) with an assessment of spatial association. Mantel's tests revealed significant spatial autocorrelation in species richness at four of the five sites sampled, indicating that richness in a plot correlated with the richness of nearby plots. We subsequently considered the degree to which spatial autocorrelations in richness could be explained by spatial autocorrelations in environmental conditions. Once data were corrected for environmental correlations, spatial autocorrelation in residual species richness could not be detected at any site. Based on these results, we conclude that in this coastal wetland, there appears to be a fine-scale mapping of diversity to microgradients in environmental conditions.

  6. A spatial interaction model with spatially structured origin and destination effects

    Science.gov (United States)

    LeSage, James P.; Llano, Carlos

    2013-07-01

    We introduce a Bayesian hierarchical regression model that extends the traditional least-squares regression model used to estimate gravity or spatial interaction relations involving origin-destination flows. Spatial interaction models attempt to explain variation in flows from n origin regions to n destination regions resulting in a sample of N = n 2 observations that reflect an n by n flow matrix converted to a vector. Explanatory variables typically include origin and destination characteristics as well as distance between each region and all other regions. Our extension introduces latent spatial effects parameters structured to follow a spatial autoregressive process. Individual effects parameters are included in the model to reflect latent or unobservable influences at work that are unique to each region treated as an origin and destination. That is, we estimate 2 n individual effects parameters using the sample of N = n 2 observations. We illustrate the method using a sample of commodity flows between 18 Spanish regions during the 2002 period.

  7. Spatial and temporal variations of thunderstorm activities over Sri Lanka

    Science.gov (United States)

    Sonnadara, Upul

    2016-05-01

    Spatial and temporal variation of frequencies of thunderstorms over Sri Lanka using thunder day data is presented. A thunder day is simply a calendar day in which thunder is heard at least once at a given location. Two sets of data were collected and analyzed: annual totals for 10 climatological stations for a period of 50 years and monthly totals for 20 climatological stations for a period of 20 years. The average annual thunder days over Sri Lanka was found to be 76. Among the climatological stations considered, a high number of annual thunder days was recorded in Ratnapura (150 days/year), followed by Colombo (108 days/year) and Bandarawela (106 days/year). It appears that there are no widespread long-term increasing or decreasing trends in thunderstorm frequencies. However, Colombo, the capital of Sri Lanka which has over two million people shows an increasing trend of 0.8 thunder days per year. Although there is a high variability between stations reporting the number of thunder days, the overall pattern within a year is clear. Thunderstorm frequencies are high during two periods: March-May and September-November, which coincide with the first inter-monsoon and second inter-monsoon periods. Compared to the dry zone, the wet zone, especially the southwestern region, has high thunderstorm activity. There is a clear spatial difference in thunderstorm activities during the southwest and northeast monsoon seasons. During both these seasons, enhanced thunderstorm activities are reported on the leeward side of the mountain range. A slight reduction in the thunderstorm activities was found in the high elevation areas of the hill country compared to the surrounding areas. A lightning ground flash density map derived using annual thunder days is also presented.

  8. Spatially resolved modelling of inhomogeneous materials with a first order magnetic phase transition

    Science.gov (United States)

    Nielsen, K. K.; Bahl, C. R. H.; Smith, A.; Bjørk, R.

    2017-10-01

    We present a numerical model that can simulate a magnetocaloric sample on the grain size level, including magnetostatics, heat transfer, local hysteresis and spatial variation of stoichiometry expressed as a variation in Curie temperature, \

  9. Temporal and spatial variations of the Huanghe River mouth bars

    Institute of Scientific and Technical Information of China (English)

    YANG Zuosheng; ZHANG Yong; LIU Zhan; WEI Helong; HE Shufeng

    2005-01-01

    On the basis of the bathymetric records of 371 survey sections in the present Huanghe mouth area from 1996 to 2001, the temporal and spatial variations of the Huanghe mouth bars were studied by using GIS technology. The variation of the mouth bars is closely related to the water and sediment discharges from the Huanghe River to the sea that has been decreasing drastically in recent years, and to coastal hydrodynamic regimes. The characteristics of the mouth bars are unique in contrast with those of other estuaries in the world (1) The mouth bars of the Huanghe River consist of many small sandbars. Usually the sandbars are of ellipse-shape with the long axis of about 1~6 km, and short axis of about 1~4 kin. The long axis is parallel to the principal direction of tidal current, and the short axis is variable, depending on the local dynamics. The crest of the sandbars is only about 0.4 m below the water surface at low tide. They are distributed within an area of 20 km2, not far from the river mouth area. The present mouth bars are in small-medium size, quite different from the large one formed during the 1970s and 1980s, when the river sediment discharge was several times larger than that after 1996. (2) The scale of a river mouth bar is related to the river discharge of that year. In 1997 sediment discharge from the Huanghe River was 42 Mt, and the mouth bar consisted of several small scattered sandbars. In 1998 the size of mouth bars was much larger thar that in 1997, as the sediment discharge from the Huanghe River increased to 363 Mt. Variation of the mouth bars largely depends on the sediment discharge with a correlation coefficient of 0.78. The calculation of the volume of the mouth bar area shows that about 30%~40% of the river's into-sea sediment is deposited in the mouth bar area. (3) Compared with other large estuaries in the world, the Huanghe mouth bars have three unique features in responding to its high sediment concentration: small size, steep

  10. Mapping Spatial and Temporal Variations of Leaf Area Index for Winter Wheat in North China

    Institute of Scientific and Technical Information of China (English)

    YANG Peng; WU Wen-bin; TANG Hua-jun; ZHOU Qing-bo; ZOU Jin-qiu; ZHANG Li

    2007-01-01

    Leaf area index(LAI)is an important parameter in a number of models related to ecosystem functioning,carbon budgets,climate,hydrology,and crop growth simulation.Mapping and monitoring the spatial and temporal variations of LAI are necessary for understanding crop growth and development at regional level.In this study.the relationships between LAI of winter wheat and Landsat TM spectral vegetation indices(SVIs)were analyzed by using the curve estimation procedure in North China Plain.The series of LAI maps retrieved by the best regression model were used to assess the spatial and temporal Variations of winter wheat LAI.The results indicated that the general relationships between LAI and SVIs were curvilinear,and that the exponential model gave a better fit than the linear model or other nonlinear models for most SVIs.The best regression model was constructed using an exponential model between surface-reflectance-derived difference vegetation index(DVI)and LAI,with the adjusted R2(0.82)and the RMSE(0.77).The TM LAI maps retrieved from DVILAI model showed the significant spatial and temporal variations.The mean TMLAI value(30m)for winter wheat of the study area increased from 1.29(March 7,2004)to 3.43(April 8,2004),with standard deviations of 0.22 and 1.17,respectively.In conclusion,spectral vegetation indices from multi-temporal Landsat TM images can be used to produce fine-resolution LAI maps for winter wheat in North China Plain.

  11. Spatial variation in atmospheric nitrogen deposition on low canopy vegetation

    Energy Technology Data Exchange (ETDEWEB)

    Verhagen, Rene [Community and Conservation Ecology Group, University of Groningen, P.O. Box 14, 9750 AA Haren (Netherlands); Diggelen, Rudy van [Community and Conservation Ecology Group, University of Groningen, P.O. Box 14, 9750 AA Haren (Netherlands)]. E-mail: r.van.diggelen@rug.nl

    2006-12-15

    Current knowledge about the spatial variation of atmospheric nitrogen deposition on a local scale is limited, especially for vegetation with a low canopy. We measured nitrogen deposition on artificial vegetation at variable distances of local nitrogen emitting sources in three nature reserves in the Netherlands, differing in the intensity of agricultural practices in the surroundings. In the nature reserve located in the most intensive agricultural region nitrogen deposition decreased with increasing distance to the local farms, until at a distance of 1500 m from the local nitrogen emitting sources the background level of 15 kg N ha{sup -1} yr{sup -1} was reached. No such trend was observed in the other two reserves. Interception was considerably lower than in woodlands and hence affected areas were larger. The results are discussed in relation to the prospects for the conservation or restoration of endangered vegetation types of nutrient-poor soil conditions. - Areas with low canopy vegetation are affected over much larger distances by nitrogen deposition than woodlands.

  12. Temporal and spatial variations in wildlife population fluctuations in Greenland; The effect of climate, environment and man

    DEFF Research Database (Denmark)

    Moshøj, Charlotte Margaret; Forchhammer, Mads C.; Forbes, Valery E.

    2009-01-01

    Temporal and spatial variations in wildlife population fluctuations in Greenland; The effect of climate, environment and man Moshøj, C.M, M.C.Forchhammer and V.E. Forbes Temporal and spatial variations in wildlife population fluctuations in Greenland; The effect of climate, environment and man...... and mammals display distinct population fluctuations of varying temporal and spatial scale. In Greenland, historical records, archaeological findings and oral accounts passed on from Inuit elders all document that the presence of wildlife species and their population sizes have undergone pronounced....... The results of this study will model future predictions of wildlife populations under changing climate variables and human hunting pressure....

  13. Spatial variation and socio-economic determinants of Plasmodium falciparum infection in northeastern Tanzania

    DEFF Research Database (Denmark)

    Mmbando, Bruno P; Kamugisha, Mathias L; Lusingu, John P;

    2011-01-01

    the country. This study describes the spatial variation and socio-economic determinants of P. falciparum infection in northeastern Tanzania. METHODS: The study was conducted in 14 villages located in highland, lowland and urban areas of Korogwe district. Four cross-sectional malaria surveys involving...... system (GPS) unit. The effects of risk factors were determined using generalized estimating equation and spatial risk of P. falciparum infection was modelled using a kernel (non-parametric) method. RESULTS: There was a significant spatial variation of P. falciparum infection, and urban areas were...

  14. Manifestations of a spatial variation of fundamental constants on atomic clocks, Oklo, meteorites, and cosmological phenomena

    CERN Document Server

    Berengut, J C

    2010-01-01

    The remarkable detection of a spatial variation in the fine-structure constant, alpha, from quasar absorption systems must be independently confirmed by complementary searches. In this letter, we discuss how terrestrial measurements of time-variation of the fundamental constants in the laboratory, meteorite data, and analysis of the Oklo nuclear reactor can be used to corroborate the spatial variation seen by astronomers. Furthermore, we show that spatial variation of the fundamental constants may be observable as spatial anisotropy in the cosmic microwave background, the accelerated expansion (dark energy), and large-scale structure of the Universe.

  15. Integrated spatial sampling modeling of geospatial data

    Institute of Scientific and Technical Information of China (English)

    LI Lianfa; WANG Jinfeng

    2004-01-01

    Spatial sampling is a necessary and important method for extracting geospatial data and its methodology directly affects the geo-analysis results. Counter to the deficiency of separate models of spatial sampling, this article analyzes three crucial elements of spatial sampling (frame, correlation and decision diagram) and induces its general integrated model. The program of Spatial Sampling Integration (SSI) has been developed with Component Object Model (COM) to realize the general integrated model. In two practical applications, i.e. design of the monitoring network of natural disasters and sampling survey of the areas of non-cultivated land, SSI has produced accurate results at less cost, better realizing the cost-effective goal of sampling toward the geo-objects with spatial correlation. The two cases exemplify expanded application and convenient implementation of the general integrated model with inset components in an integrated environment, which can also be extended to other modeling of spatial analysis.

  16. Geographic variations in cervical cancer risk in San Luis Potosí state, Mexico: A spatial statistical approach.

    Science.gov (United States)

    Terán-Hernández, Mónica; Ramis-Prieto, Rebeca; Calderón-Hernández, Jaqueline; Garrocho-Rangel, Carlos Félix; Campos-Alanís, Juan; Ávalos-Lozano, José Antonio; Aguilar-Robledo, Miguel

    2016-09-29

    Worldwide, Cervical Cancer (CC) is the fourth most common type of cancer and cause of death in women. It is a significant public health problem, especially in low and middle-income/Gross Domestic Product (GDP) countries. In the past decade, several studies of CC have been published, that identify the main modifiable and non-modifiable CC risk factors for Mexican women. However, there are no studies that attempt to explain the residual spatial variation in CC incidence In Mexico, i.e. spatial variation that cannot be ascribed to known, spatially varying risk factors. This paper uses a spatial statistical methodology that takes into account spatial variation in socio-economic factors and accessibility to health services, whilst allowing for residual, unexplained spatial variation in risk. To describe residual spatial variations in CC risk, we used generalised linear mixed models (GLMM) with both spatially structured and unstructured random effects, using a Bayesian approach to inference. The highest risk is concentrated in the southeast, where the Matlapa and Aquismón municipalities register excessive risk, with posterior probabilities greater than 0.8. The lack of coverage of Cervical Cancer-Screening Programme (CCSP) (RR 1.17, 95 % CI 1.12-1.22), Marginalisation Index (RR 1.05, 95 % CI 1.03-1.08), and lack of accessibility to health services (RR 1.01, 95 % CI 1.00-1.03) were significant covariates. There are substantial differences between municipalities, with high-risk areas mainly in low-resource areas lacking accessibility to health services for CC. Our results clearly indicate the presence of spatial patterns, and the relevance of the spatial analysis for public health intervention. Ignoring the spatial variability means to continue a public policy that does not tackle deficiencies in its national CCSP and to keep disadvantaging and disempowering Mexican women in regard to their health care.

  17. Spatial and temporal variations of new particle formation in East Asia using an NPF-explicit WRF-chem model: North-south contrast in new particle formation frequency

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, H.; Koike, Makoto; Takegawa, Nobuyuki; Kondo, Yutaka; Takami, A.; Takamura, T.; Yoon, Soh-joung; Kim, S. W.; Lim, Hyuntae; Fast, Jerome D.

    2013-10-27

    The new particle formation (NPF)-explicit version of the WRF-chem model, which we developed recently, can calculate the growth and sink of nucleated clusters explicitly with 20 aerosol size bins from 1 nm to 10 μm. In this study, the model is used to understand spatial and temporal variations of the frequency of NPF events and the concentrations of aerosols (condensation nuclei, CN) and cloud condensation nuclei (CCN) within the boundary layer in East Asia in spring 2009. Model simulations show distinct north-south contrast in the frequency and mechanism of NPF in East Asia. NPF mostly occurred over limited periods and regions between 30° and 45°N, such as northeast China, Korea, and Japan, including regions around active volcanoes (Miyakejima and Sakurajima). At these latitudes, NPF was considerably suppressed by high concentrations of preexisting particles under stagnant air conditions associated with high-pressure systems, while nucleation occurred more extensively on most days during the simulation period. Conversely, neither nucleation nor NPF occurred frequently south of 30°N because of lower SO2 emissions and H2SO4 concentrations. The period-averaged NPF frequency was 3 times higher at latitudes of 30° - 45°N than at latitudes of 20° - 30°N. The north-south contrast of NPF frequency is validated by surface measurements in outflow regions in East Asia. The period- and domain-averaged contribution of secondary particles is estimated to be 44% for CN (> 10 nm) and 26% for CCN at a supersaturation of 1.0% in our simulation, though the contribution is highly sensitive to the magnitudes and size distributions of primary aerosol emissions and the coefficients in the nucleation parameterizations.

  18. Spatial and temporal variations in mango colour, acidity, and sweetness in relation to temperature and ethylene gradients within the fruit.

    Science.gov (United States)

    Nordey, Thibault; Léchaudel, Mathieu; Génard, Michel; Joas, Jacques

    2014-11-01

    Managing fruit quality is complex because many different attributes have to be taken into account, which are themselves subjected to spatial and temporal variations. Heterogeneous fruit quality has been assumed to be partly related to temperature and maturity gradients within the fruit. To test this assumption, we measured the spatial variability of certain mango fruit quality traits: colour of the peel and of the flesh, and sourness and sweetness, at different stages of fruit maturity using destructive methods as well as vis-NIR reflectance. The spatial variability of mango quality traits was compared to internal variations in thermal time, simulated by a physical model, and to internal variations in maturity, using ethylene content as an indicator. All the fruit quality indicators analysed showed significant spatial and temporal variations, regardless of the measurement method used. The heterogeneity of internal fruit quality traits was not correlated with the marked internal temperature gradient we modelled. However, variations in ethylene content revealed a strong internal maturity gradient which was correlated with the spatial variations in measured mango quality traits. Nonetheless, alone, the internal maturity gradient did not explain the variability of fruit quality traits, suggesting that other factors, such as gas, abscisic acid and water gradients, are also involved.

  19. Random spatial processes and geostatistical models for soil variables

    Science.gov (United States)

    Lark, R. M.

    2009-04-01

    Geostatistical models of soil variation have been used to considerable effect to facilitate efficient and powerful prediction of soil properties at unsampled sites or over partially sampled regions. Geostatistical models can also be used to investigate the scaling behaviour of soil process models, to design sampling strategies and to account for spatial dependence in the random effects of linear mixed models for spatial variables. However, most geostatistical models (variograms) are selected for reasons of mathematical convenience (in particular, to ensure positive definiteness of the corresponding variables). They assume some underlying spatial mathematical operator which may give a good description of observed variation of the soil, but which may not relate in any clear way to the processes that we know give rise to that observed variation in the real world. In this paper I shall argue that soil scientists should pay closer attention to the underlying operators in geostatistical models, with a view to identifying, where ever possible, operators that reflect our knowledge of processes in the soil. I shall illustrate how this can be done in the case of two problems. The first exemplar problem is the definition of operators to represent statistically processes in which the soil landscape is divided into discrete domains. This may occur at disparate scales from the landscape (outcrops, catchments, fields with different landuse) to the soil core (aggregates, rhizospheres). The operators that underly standard geostatistical models of soil variation typically describe continuous variation, and so do not offer any way to incorporate information on processes which occur in discrete domains. I shall present the Poisson Voronoi Tessellation as an alternative spatial operator, examine its corresponding variogram, and apply these to some real data. The second exemplar problem arises from different operators that are equifinal with respect to the variograms of the

  20. Spatial-Temporal Correlation Properties of the 3GPP Spatial Channel Model and the Kronecker MIMO Channel Model

    Directory of Open Access Journals (Sweden)

    Wu Hanguang

    2007-01-01

    Full Text Available The performance of multiple-input multiple-output (MIMO systems is greatly influenced by the spatial-temporal correlation properties of the underlying MIMO channels. This paper investigates the spatial-temporal correlation characteristics of the spatial channel model (SCM in the Third Generation Partnership Project (3GPP and the Kronecker-based stochastic model (KBSM at three levels, namely, the cluster level, link level, and system level. The KBSM has both the spatial separability and spatial-temporal separability at all the three levels. The spatial-temporal separability is observed for the SCM only at the system level, but not at the cluster and link levels. The SCM shows the spatial separability at the link and system levels, but not at the cluster level since its spatial correlation is related to the joint distribution of the angle of arrival (AoA and angle of departure (AoD. The KBSM with the Gaussian-shaped power azimuth spectrum (PAS is found to fit best the 3GPP SCM in terms of the spatial correlations. Despite its simplicity and analytical tractability, the KBSM is restricted to model only the average spatial-temporal behavior of MIMO channels. The SCM provides more insights of the variations of different MIMO channel realizations, but the implementation complexity is relatively high.

  1. Spatial-Temporal Correlation Properties of the 3GPP Spatial Channel Model and the Kronecker MIMO Channel Model

    Directory of Open Access Journals (Sweden)

    Cheng-Xiang Wang

    2007-02-01

    Full Text Available The performance of multiple-input multiple-output (MIMO systems is greatly influenced by the spatial-temporal correlation properties of the underlying MIMO channels. This paper investigates the spatial-temporal correlation characteristics of the spatial channel model (SCM in the Third Generation Partnership Project (3GPP and the Kronecker-based stochastic model (KBSM at three levels, namely, the cluster level, link level, and system level. The KBSM has both the spatial separability and spatial-temporal separability at all the three levels. The spatial-temporal separability is observed for the SCM only at the system level, but not at the cluster and link levels. The SCM shows the spatial separability at the link and system levels, but not at the cluster level since its spatial correlation is related to the joint distribution of the angle of arrival (AoA and angle of departure (AoD. The KBSM with the Gaussian-shaped power azimuth spectrum (PAS is found to fit best the 3GPP SCM in terms of the spatial correlations. Despite its simplicity and analytical tractability, the KBSM is restricted to model only the average spatial-temporal behavior of MIMO channels. The SCM provides more insights of the variations of different MIMO channel realizations, but the implementation complexity is relatively high.

  2. Continuous Spatial Process Models for Spatial Extreme Values

    KAUST Repository

    Sang, Huiyan

    2010-01-28

    We propose a hierarchical modeling approach for explaining a collection of point-referenced extreme values. In particular, annual maxima over space and time are assumed to follow generalized extreme value (GEV) distributions, with parameters μ, σ, and ξ specified in the latent stage to reflect underlying spatio-temporal structure. The novelty here is that we relax the conditionally independence assumption in the first stage of the hierarchial model, an assumption which has been adopted in previous work. This assumption implies that realizations of the the surface of spatial maxima will be everywhere discontinuous. For many phenomena including, e. g., temperature and precipitation, this behavior is inappropriate. Instead, we offer a spatial process model for extreme values that provides mean square continuous realizations, where the behavior of the surface is driven by the spatial dependence which is unexplained under the latent spatio-temporal specification for the GEV parameters. In this sense, the first stage smoothing is viewed as fine scale or short range smoothing while the larger scale smoothing will be captured in the second stage of the modeling. In addition, as would be desired, we are able to implement spatial interpolation for extreme values based on this model. A simulation study and a study on actual annual maximum rainfall for a region in South Africa are used to illustrate the performance of the model. © 2009 International Biometric Society.

  3. Modelling evolution in a spatial continuum

    Science.gov (United States)

    Barton, N. H.; Etheridge, A. M.; Véber, A.

    2013-01-01

    We survey a class of models for spatially structured populations which we have called spatial Λ-Fleming-Viot processes. They arise from a flexible framework for modelling in which the key innovation is that random genetic drift is driven by a Poisson point process of spatial 'events'. We demonstrate how this overcomes some of the obstructions to modelling populations which evolve in two-(and higher-) dimensional spatial continua, how its predictions match phenomena observed in data and how it fits with classical models. Finally we outline some directions for future research.

  4. Spatial variation in nutrient and water color effects on lake chlorophyll at macroscales

    Science.gov (United States)

    Fergus, C. Emi; Finley, Andrew O.; Soranno, Patricia A.; Wagner, Tyler

    2016-01-01

    The nutrient-water color paradigm is a framework to characterize lake trophic status by relating lake primary productivity to both nutrients and water color, the colored component of dissolved organic carbon. Total phosphorus (TP), a limiting nutrient, and water color, a strong light attenuator, influence lake chlorophyll a concentrations (CHL). But, these relationships have been shown in previous studies to be highly variable, which may be related to differences in lake and catchment geomorphology, the forms of nutrients and carbon entering the system, and lake community composition. Because many of these factors vary across space it is likely that lake nutrient and water color relationships with CHL exhibit spatial autocorrelation, such that lakes near one another have similar relationships compared to lakes further away. Including this spatial dependency in models may improve CHL predictions and clarify how well the nutrient-water color paradigm applies to lakes distributed across diverse landscape settings. However, few studies have explicitly examined spatial heterogeneity in the effects of TP and water color together on lake CHL. In this study, we examined spatial variation in TP and water color relationships with CHL in over 800 north temperate lakes using spatially-varying coefficient models (SVC), a robust statistical method that applies a Bayesian framework to explore space-varying and scale-dependent relationships. We found that TP and water color relationships were spatially autocorrelated and that allowing for these relationships to vary by individual lakes over space improved the model fit and predictive performance as compared to models that did not vary over space. The magnitudes of TP effects on CHL differed across lakes such that a 1 μg/L increase in TP resulted in increased CHL ranging from 2–24 μg/L across lake locations. Water color was not related to CHL for the majority of lakes, but there were some locations where water color had a

  5. Spatial and temporal variations in airborne Ambrosia pollen in Europe.

    Science.gov (United States)

    Sikoparija, B; Skjøth, C A; Celenk, S; Testoni, C; Abramidze, T; Alm Kübler, K; Belmonte, J; Berger, U; Bonini, M; Charalampopoulos, A; Damialis, A; Clot, B; Dahl, Å; de Weger, L A; Gehrig, R; Hendrickx, M; Hoebeke, L; Ianovici, N; Kofol Seliger, A; Magyar, D; Mányoki, G; Milkovska, S; Myszkowska, D; Páldy, A; Pashley, C H; Rasmussen, K; Ritenberga, O; Rodinkova, V; Rybníček, O; Shalaboda, V; Šaulienė, I; Ščevková, J; Stjepanović, B; Thibaudon, M; Verstraeten, C; Vokou, D; Yankova, R; Smith, M

    2017-01-01

    The European Commission Cooperation in Science and Technology (COST) Action FA1203 "SMARTER" aims to make recommendations for the sustainable management of Ambrosia across Europe and for monitoring its efficiency and cost-effectiveness. The goal of the present study is to provide a baseline for spatial and temporal variations in airborne Ambrosia pollen in Europe that can be used for the management and evaluation of this noxious plant. The study covers the full range of Ambrosia artemisiifolia L. distribution over Europe (39°N-60°N; 2°W-45°E). Airborne Ambrosia pollen data for the principal flowering period of Ambrosia (August-September) recorded during a 10-year period (2004-2013) were obtained from 242 monitoring sites. The mean sum of daily average airborne Ambrosia pollen and the number of days that Ambrosia pollen was recorded in the air were analysed. The mean and standard deviation (SD) were calculated regardless of the number of years included in the study period, while trends are based on those time series with 8 or more years of data. Trends were considered significant at p < 0.05. There were few significant trends in the magnitude and frequency of atmospheric Ambrosia pollen (only 8% for the mean sum of daily average Ambrosia pollen concentrations and 14% for the mean number of days Ambrosia pollen were recorded in the air). The direction of any trends varied locally and reflected changes in sources of the pollen, either in size or in distance from the monitoring station. Pollen monitoring is important for providing an early warning of the expansion of this invasive and noxious plant.

  6. Spatial variation in reproductive effort of a southern Australian seagrass.

    Science.gov (United States)

    Smith, Timothy M; York, Paul H; Macreadie, Peter I; Keough, Michael J; Ross, D Jeff; Sherman, Craig D H

    2016-09-01

    In marine environments characterised by habitat-forming plants, the relative allocation of resources into vegetative growth and flowering is an important indicator of plant condition and hence ecosystem health. In addition, the production and abundance of seeds can give clues to local resilience. Flowering density, seed bank, biomass and epiphyte levels were recorded for the temperate seagrass Zostera nigricaulis in Port Phillip Bay, south east Australia at 14 sites chosen to represent several regions with different physicochemical conditions. Strong regional differences were found within the large bay. Spathe and seed density were very low in the north of the bay (3 sites), low in the centre of the bay (2 sites) intermediate in the Outer Geelong Arm (2 sites), high in Swan Bay (2 sites) and very high in the Inner Geelong Arm (3 sites). In the south (2 sites) seed density was low and spathe density was high. These regional patterns were largely consistent for the 5 sites sampled over the three year period. Timing of flowering was consistent across sites, occurring from August until December with peak production in October, except during the third year of monitoring when overall densities were lower and peaked in November. Seagrass biomass, epiphyte load, canopy height and stem density showed few consistent spatial and temporal patterns. Variation in spathe and seed density and morphology across Port Phillip Bay reflects varying environmental conditions and suggests that northern sites may be restricted in their ability to recover from disturbance through sexual reproduction. In contrast, sites in the west and south of the bay have greater potential to recover from disturbances due to a larger seed bank and these sites could act as source populations for sites where seed production is low.

  7. Analysis of spatial and yearly variation in winter survival of winter wheat

    Science.gov (United States)

    Hayhoe, H. N.; Andrews, C. J.

    Four years of winter survival data for winter wheat (Triticum aestivum L.) were collected on a loam soil located on the Central Experimental Farm at Ottawa, Ontario (45° 23'N, 75° 43'W). The site was low-lying and subject to frequent winter flooding and ice sheet formation. It appeared level although there was microtopographic variation with a range in elevation of approximately 0.15 m. The objective of the study was to gain insight into factors which might affect winter survival. Two varieties, a soft white and a hard red winter wheat, were planted in September. Crop establishment was measured in late fall and the percentage survival was measured in April of the following year. We assumed the large spatial differences in survival were not totally random, but rather were affected by spatial variation in environmental factors such as snow and ice depth, soil moisture and temperature. Hourly measurements of soil temperature at a depth of 0.05 m were recorded throughout the fall, winter and spring. Fall and spring soil moisture at the same depth were measured on the plot, as well as snow and ice depth at selected times throughout the winter. Measurements were taken on a grid covering the plot to help explain spatial variation in survival. In addition, detailed measurements of elevation were taken on a grid. Meteorological data were available from the nearby weather site. While soil temperatures were never low enough to kill plants according to the CERES model, the spatial variation in winter survival was associated with differences in elevation and the resulting surface drainage patterns.

  8. A quantitative framework to estimate the relative importance of environment, spatial variation and patch connectivity in driving community composition.

    Science.gov (United States)

    Monteiro, Viviane F; Paiva, Paulo C; Peres-Neto, Pedro R

    2017-03-01

    Perhaps the most widely used quantitative approach in metacommunity ecology is the estimation of the importance of local environment vs. spatial structuring using the variation partitioning framework. Contrary to metapopulation models, however, current empirical studies of metacommunity structure using variation partitioning assume a space-for-dispersal substitution due to the lack of analytical frameworks that incorporate patch connectivity predictors of dispersal dynamics. Here, a method is presented that allows estimating the relative importance of environment, spatial variation and patch connectivity in driving community composition variation within metacommunities. The proposed approach is illustrated by a study designed to understand the factors driving the structure of a soft-bottom marine polychaete metacommunity. Using a standard variation partitioning scheme (i.e. where only environmental and spatial predictors are used), only about 13% of the variation in metacommunity structure was explained. With the connectivity set of predictors, the total amount of explained variation increased up to 51% of the variation. These results highlight the importance of considering predictors of patch connectivity rather than just spatial predictors. Given that information on connectivity can be estimated by commonly available data on species distributions for a number of taxa, the framework presented here can be readily applied to past studies as well, facilitating a more robust evaluation of the factors contributing to metacommunity structure.

  9. Study on temporal variation and spatial distribution for rural poverty in China based on GIS

    Science.gov (United States)

    Feng, Xianfeng; Xu, Xiuli; Wang, Yingjie; Cui, Jing; Mo, Hongyuan; Liu, Ling; Yan, Hong; Zhang, Yan; Han, Jiafu

    2009-07-01

    Poverty is one of the most serious challenges all over the world, is an obstacle to hinder economics and agriculture in poverty area. Research on poverty alleviation in China is very useful and important. In this paper, we will explore the comprehensive poverty characteristics in China, analyze the current poverty status, spatial distribution and temporal variations about rural poverty in China, and to category the different poverty types and their spatial distribution. First, we achieved the gathering and processing the relevant data. These data contain investigation data, research reports, statistical yearbook, censuses, social-economic data, physical and anthrop geographical data, etc. After deeply analysis of these data, we will get the distribution of poverty areas by spatial-temporal data model according to different poverty given standard in different stages in China to see the poverty variation and the regional difference in County-level. Then, the current poverty status, spatial pattern about poverty area in villages-level will be lucubrated; the relationship among poverty, environment (including physical and anthrop geographical factors) and economic development, etc. will be expanded. We hope our research will enhance the people knowledge of poverty in China and contribute to the poverty alleviation in China.

  10. Local models for spatial analysis

    CERN Document Server

    Lloyd, Christopher D

    2010-01-01

    Focusing on solutions, this second edition provides guidance to a wide variety of real-world problems. The text presents a complete introduction to key concepts and a clear mapping of the methods discussed. It also explores connections between methods. New chapters address spatial patterning in single variables and spatial relations. In addition, every chapter now includes links to key related studies. The author clearly distinguishes between local and global methods and provides more detailed coverage of geographical weighting, image texture measures, local spatial autocorrelation, and multic

  11. Persistent organic pollutants in the atmosphere - spatial and temporal variations

    Energy Technology Data Exchange (ETDEWEB)

    Backe, Cecilia

    2001-05-01

    In this thesis I have studied the spatial and temporal variations of PCBs in the atmosphere and in precipitation in southern Sweden. Further, soil-air exchange processes of PCBs were investigated. Finally, the long-range transport of PCBs and DDT was studied in the Baltic Sea region and in a tropical vs. a temporal region. On the regional scale there were significant differences in PCB concentration in the atmosphere, in precipitation and in soil between nearby sampling-areas. Differences in PCB concentrations between areas probably originated from varying geographical and meteorological conditions that affected exchange processes between air and soil/vegetation surfaces. Temporal variations in PCB concentration in atmosphere and precipitation were also found. For PCBs in the air, a systematic pattern in the deviation from the yearly median value for the region was observed. Wind direction played an important role for PCB concentration in precipitation in coastal areas, while at the inland sites this variable seemed to have a minor influence. To examine the intensity of precipitation scavenging, the total washout ratios were calculated and the highest ratios were observed at the two sites where PCB concentration in the air was high. Further, high concentrations of PCB in precipitation correlated with a composition of highly chlorinated PCB congeners, as shown by principal component analysis. For most of the sites there was a significant negative relationship between PCB concentration and rain volume. Soil type and soil organic matter content was found to be important for the variations in PCB concentration between nearby areas. Highest concentrations were found at two sites with sandy soils, one with an extremely high organic carbon content. Soils with similar soil textures (i.e. sandy silt moraine) did not show any significant differences in PCB concentrations. PCB congener composition was shown to differ between sites, with site-specific congener patterns. No

  12. Spatial and temporal variations of new particle formation in East Asia using an NPF-explicit WRF-chem model: North-south contrast in new particle formation frequency

    Science.gov (United States)

    Matsui, H.; Koike, M.; Takegawa, N.; Kondo, Y.; Takami, A.; Takamura, T.; Yoon, S.; Kim, S.-W.; Lim, H.-C.; Fast, J. D.

    2013-10-01

    recently developed new particle formation (NPF)-explicit version of the Weather Research and Forecasting Chemistry (WRF-chem) model can explicitly calculate the growth and sink of nucleated clusters with 20 aerosol size bins from 1 nm to 10 µm in diameter. In this study, the model was used to investigate spatial and temporal variations in NPF event frequency and the concentrations of aerosols (condensation nuclei, CN) and cloud condensation nuclei (CCN) within the boundary layer in East Asia in spring 2009. We found a distinct north-south contrast in the NPF frequency and mechanism in East Asia. NPF occurred mainly during limited periods over certain regions between 30° and 45°N (northeast China, Korea, and Japan, including regions around the active volcanoes Miyakejima and Sakurajima). In these latitudes, NPF was suppressed by high concentrations of preexisting particles under stagnant air conditions associated with high-pressure systems, although nucleation occurred more extensively during most of the simulation period. In contrast, south of 30°N, nucleation and NPF were both infrequent because of low SO2 emissions and H2SO4 concentrations. The period-averaged NPF frequency at 30°-45°N was three times that at 20°-30°N. This north-south contrast in NPF frequency was validated by surface measurements in outflow regions of East Asia. The simulated period- and domain-averaged contribution of secondary particles was estimated to be 44% for CN (>10 nm) and 26% for CCN at a supersaturation of 1.0%, though the contribution was highly sensitive to the amount and size distribution of primary aerosol emissions and the rate coefficient of the nucleation parameterization.

  13. Roles of climate, vegetation and soil in regulating the spatial variations in ecosystem carbon dioxide fluxes in the Northern Hemisphere.

    Directory of Open Access Journals (Sweden)

    Zhi Chen

    Full Text Available Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP, annual ecosystem respiration (ARE, and annual net ecosystem production (ANEP. Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P 0.05 in the Northern Hemisphere. The climate and vegetation together explained 60% and 58% of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation could account for 45-47% of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75%. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances is necessary.

  14. Spatial and temporal variations of microbial properties at different scales in shallow subsurface sediments.

    Science.gov (United States)

    Zhang, C; Lehman, R M; Pfiffner, S M; Scarborough, S P; Palumbo, A V; Phelps, T J; Beauchamp, J J; Colwell, F S

    1997-01-01

    Microbial abundance, activity, and community-level physiological profiles (CLPP) were examined at centimeter and meter scales in the subsurface environment at a site near Oyster, VA. At the centimeter scale, variations in aerobic culturable heterotrophs (ACH) and glucose mineralization rates (GMR) were highest in the water table zone, indicating that water availability has a major effect on variations in microbial abundance and activity. At the meter scale, ACH and microaerophiles decreased significantly with depth, whereas anaerobic GMR often increased with depth; this may indicate low redox potentials at depth caused by microbial consumption of oxygen. Data of CLPP indicated that the microbial community (MC) in the soybean field exhibited greater capability to utilize multiple carbon sources than MC in the corn field. This difference may reflect nutrient availability associated with different crops (soybean vs corn). By using a regression model, significant spatial and temporal variations were observed for ACH, microaerophiles, anaerobic GMR, and CLPP. Results of this study indicated that water and nutrient availability as well as land use could have a dominant effect on spatial and temporal variations in microbial properties in shallow subsurface environments.

  15. KING GEORGE ISLAND SPATIAL DATA MODEL

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Distribution,interoperability,interactivity,component are four main features of distributed GIS.Based on the principle of hypermap,hypermedia and distributed database,the paper comes up with a kind of distributed spatial data model which is in accordance with those features of distributed GIS.The model takes catalog service as the outline of spatial information globalization,and defines data structure of hypermap node in different level.Based on the model,it is feasible to manage and process distributed spatial information,and integrate multi_source,heterogeneous spatial data into a framework.Traditionally,to retrieve and access spatial data via Internet is only by theme or map name.With the concept of the model,it is possible to retrieve,load,and link spatial data by vector_based graphics on the Internet.

  16. Bayesian Spatial Modelling with R-INLA

    Directory of Open Access Journals (Sweden)

    Finn Lindgren

    2015-02-01

    Full Text Available The principles behind the interface to continuous domain spatial models in the R- INLA software package for R are described. The integrated nested Laplace approximation (INLA approach proposed by Rue, Martino, and Chopin (2009 is a computationally effective alternative to MCMC for Bayesian inference. INLA is designed for latent Gaussian models, a very wide and flexible class of models ranging from (generalized linear mixed to spatial and spatio-temporal models. Combined with the stochastic partial differential equation approach (SPDE, Lindgren, Rue, and Lindstrm 2011, one can accommodate all kinds of geographically referenced data, including areal and geostatistical ones, as well as spatial point process data. The implementation interface covers stationary spatial mod- els, non-stationary spatial models, and also spatio-temporal models, and is applicable in epidemiology, ecology, environmental risk assessment, as well as general geostatistics.

  17. Variations in cardiovascular disease under-diagnosis in England: national cross-sectional spatial analysis

    Directory of Open Access Journals (Sweden)

    Walford Hannah

    2011-03-01

    Full Text Available Abstract Background There is under-diagnosis of cardiovascular disease (CVD in the English population, despite financial incentives to encourage general practices to register new cases. We compared the modelled (expected and diagnosed (observed prevalence of three cardiovascular conditions- coronary heart disease (CHD, hypertension and stroke- at local level, their geographical variation, and population and healthcare predictors which might influence diagnosis. Methods Cross-sectional observational study in all English local authorities (351 and general practices (8,372 comparing model-based expected prevalence with diagnosed prevalence on practice disease registers. Spatial analyses were used to identify geographic clusters and variation in regression relationships. Results A total of 9,682,176 patients were on practice CHD, stroke and transient ischaemic attack, and hypertension registers. There was wide spatial variation in observed: expected prevalence ratios for all three diseases, with less than five per cent of expected cases diagnosed in some areas. London and the surrounding area showed statistically significant discrepancies in observed: expected prevalence ratios, with observed prevalence much lower than the epidemiological models predicted. The addition of general practitioner supply as a variable yielded stronger regression results for all three conditions. Conclusions Despite almost universal access to free primary healthcare, there may be significant and highly variable under-diagnosis of CVD across England, which can be partially explained by persistent inequity in GP supply. Disease management studies should consider the possible impact of under-diagnosis on population health outcomes. Compared to classical regression modelling, spatial analytic techniques can provide additional information on risk factors for under-diagnosis, and can suggest where healthcare resources may be most needed.

  18. Spatial variation in near-ground radiation and low temperature. Interactions with forest vegetation

    Energy Technology Data Exchange (ETDEWEB)

    Blennow, K.

    1997-10-01

    Low temperature has a large impact on the survival and distribution of plants. Interactive effects with high irradiance lead to cold-induced photo inhibition, which may impact on the establishment and growth of tree seedlings. In this thesis, novel approaches are applied for relating the spatial variability in low temperature and irradiance to photosynthetic performance and growth of tree seedlings, and for modelling the micro- and local-scale spatial variations in low temperature for heterogeneous terrain. The methodologies include the development and use of a digital image analysis system for hemispherical photographs, the use of Geographic Information Systems (GIS) and statistical methods, field data acquisition of meteorological elements, plant structure, growth and photosynthetic performance. Temperature and amounts of intercepted direct radiant energy for seedlings on clear days (IDRE) were related to chlorophyll a fluorescence, and the dry weight of seedlings. The combination of increased IDRE with reduced minimum temperatures resulted in persistent and strong photo inhibition as the season progressed, with likely implications for the establishment of tree seedlings at forest edges, and within shelter wood. For models of spatial distribution of low air temperature, the sky view factor was used to parameterize the radiative cooling, whilst drainage, ponding and stagnation of cold air, and thermal properties of the ground were all considered. The models hint at which scales and processes govern the development of spatial variations in low temperature for the construction of corresponding mechanistic models. The methodology is well suited for detecting areas that will be frost prone after clearing of forest and for comparing the magnitudes of impacts on low air temperature of forest management practices, such as shelter wood and soil preparation. The results can be used to formulate ground rules for use in practical forestry 141 refs, 5 figs, 1 tab

  19. Spatial variation of crustal coda Q in California

    Science.gov (United States)

    Philips, W.S.; Lee, W.H.K.; Newberry, J.T.

    1988-01-01

    Coda wave data from California microearthquakes were studied in order to delineate regional fluctuations of apparent crustal attenuation in the band 1.5 to 24 Hz. Apparent attenuation was estimated using a single back scattering model of coda waves. The coda wave data were restricted to ???30 s following the origin time; this insures that crustal effects dominate the results as the backscattered shear waves thought to form the coda would not have had time to penetrate much deeper. Results indicate a strong variation in apparent crustal attenuation at high frequencies between the Franciscan and Salinian regions of central California and the Long Valley area of the Sierra Nevada. Although the coda Q measurements coincide at 1.5 Hz (Qc=100), at 24 Hz there is a factor of four difference between the measurements made in Franciscan (Qc=525) and Long Valley (Qc=2100) with the Salinian midway between (Qc=900). These are extremely large variations compared to measures of seismic velocities of comparable resolution, demonstrating the exceptional sensitivity of the high frequency coda Q measurement to regional geology. In addition, the frequency trend of the results is opposite to that seen in a compilation of coda Q measurements made worldwide by other authors which tend to converge at high and diverge at low frequencies, however, the worldwide results generally were obtained without limiting the coda lengths and probably reflect upper mantle rather than crustal properties. Our results match those expected due to scattering in random media represented by Von Karman autocorrelation functions of orders 1/2 to 1/3. The Von Karman medium of order 1/3 corresponding to the Franciscan coda Q measurement contains greater amounts of high wavenumber fluctuations. This indicates relatively large medium fluctuations with wavelengths on the order of 100 m in the highly deformed crust associated with the Franciscan, however, the influence of scattering on the coda Q measurement is

  20. Spatial variation of the cooling lines in the Orion Bar from Herschel/PACS

    CERN Document Server

    Bernard-Salas, J; Arab, H; Abergel, A; Dartois, E; Martin, P; Bontemp, S; Joblin, C; White, G J; Bernard, J -P; Naylor, D

    2011-01-01

    We present spatially resolved Herschel/PACS observations of the Orion Bar. We have characterise the emission of the far-infrared fine-structure lines of [CII] (158um), [OI] (63 and 145um), and [NII] (122um) that trace the gas local conditions. The observed distribution and variation of the lines are discussed in relation to the underlying geometry and linked to the energetics associated with the Trapezium stars. These observations enable us to map the spatial distribution of these fine-structure lines with a spatial resolution between 4" and 11" and covering a total square area of about 120"x105". The spatial profile of the emission lines are modelled using the radiative transfer code Cloudy. We find that the spatial distribution of the [CII] line coincides with that of the [OI] lines. The [NII] line peaks closer to the ionising star than the other three lines, but with a small region of overlap. We can distinguish several knots of enhanced emission within the Bar indicating the presence of an inhomogenous an...

  1. Dynamic spatial panels : models, methods, and inferences

    NARCIS (Netherlands)

    Elhorst, J. Paul

    This paper provides a survey of the existing literature on the specification and estimation of dynamic spatial panel data models, a collection of models for spatial panels extended to include one or more of the following variables and/or error terms: a dependent variable lagged in time, a dependent

  2. Continuous-Time Modeling with Spatial Dependence

    NARCIS (Netherlands)

    Oud, J.H.L.; Folmer, H.; Patuelli, R.; Nijkamp, P.

    2012-01-01

    (Spatial) panel data are routinely modeled in discrete time (DT). However, compelling arguments exist for continuous-time (CT) modeling of (spatial) panel data. Particularly, most social processes evolve in CT, so that statistical analysis in DT is an oversimplification, gives an incomplete

  3. Continuous-Time Modeling with Spatial Dependence

    NARCIS (Netherlands)

    Oud, J.; Folmer, H.; Patuelli, R.; Nijkamp, P.

    (Spatial) panel data are routinely modeled in discrete time (DT). However, compelling arguments exist for continuous-time (CT) modeling of (spatial) panel data. Particularly, most social processes evolve in CT, so that statistical analysis in DT is an oversimplification, gives an incomplete

  4. Spatial and seasonal variations in evapotranspiration over Canada's landmass

    Directory of Open Access Journals (Sweden)

    S. Wang

    2013-05-01

    Full Text Available A 30 yr (1979–2008 dataset of actual evapotranspiration (ET at 1 km resolution was generated over Canada's landmass by integrating remote sensing land surface data and gridded climate data using the EALCO model run at 30 min time step. This long-term high resolution dataset was used to characterize the spatiotemporal variations in ET across Canada. The results show that annual ET varied from 600 mm yr−1 over several regions in the south to less than 100 mm yr−1 in the northern arctic. Nationally, ET in summer (i.e., June to August comprised 65% of the annual total amount. ET in the cold season remained mostly below 10 mm month−1 over the country. Negative monthly ET was obtained over the arctic region in winter, indicating EALCO simulated a larger amount of condensation than ET. Overall, the mean ET over the entire Canadian landmass for the 30 yr was 239 mm yr−1, or 44% of its corresponding precipitation. Comparisons of available ET studies in Canada revealed large uncertainties in ET estimates associated with using different approaches. The scarcity of ET measurements for the diverse ecosystems in Canada remains a significant challenge for reducing the uncertainties; this gap needs to be addressed in future studies to improve capabilities in climate/weather modelling and water resource management.

  5. Local variations in spatial synchrony of influenza epidemics.

    Directory of Open Access Journals (Sweden)

    James H Stark

    Full Text Available BACKGROUND: Understanding the mechanism of influenza spread across multiple geographic scales is not complete. While the mechanism of dissemination across regions and states of the United States has been described, understanding the determinants of dissemination between counties has not been elucidated. The paucity of high resolution spatial-temporal influenza incidence data to evaluate disease structure is often not available. METHODOLOGY AND FINDINGS: We report on the underlying relationship between the spread of influenza and human movement between counties of one state. Significant synchrony in the timing of epidemics exists across the entire state and decay with distance (regional correlation=62%. Synchrony as a function of population size display evidence of hierarchical spread with more synchronized epidemics occurring among the most populated counties. A gravity model describing movement between two populations is a stronger predictor of influenza spread than adult movement to and from workplaces suggesting that non-routine and leisure travel drive local epidemics. CONCLUSIONS: These findings highlight the complex nature of influenza spread across multiple geographic scales.

  6. Spatial Climate Patterns Explain Negligible Variation in Strength of Compensatory Density Feedbacks in Birds and Mammals

    Science.gov (United States)

    Herrando-Pérez, Salvador; Delean, Steven; Brook, Barry W.; Cassey, Phillip; Bradshaw, Corey J. A.

    2014-01-01

    The use of long-term population data to separate the demographic role of climate from density-modified demographic processes has become a major topic of ecological investigation over the last two decades. Although the ecological and evolutionary mechanisms that determine the strength of density feedbacks are now well understood, the degree to which climate gradients shape those processes across taxa and broad spatial scales remains unclear. Intuitively, harsh or highly variable environmental conditions should weaken compensatory density feedbacks because populations are hypothetically unable to achieve or maintain densities at which social and trophic interactions (e.g., competition, parasitism, predation, disease) might systematically reduce population growth. Here we investigate variation in the strength of compensatory density feedback, from long-term time series of abundance over 146 species of birds and mammals, in response to spatial gradients of broad-scale temperature precipitation variables covering 97 localities in 28 countries. We use information-theoretic metrics to rank phylogenetic generalized least-squares regression models that control for sample size (time-series length) and phylogenetic non-independence. Climatic factors explained < 1% of the remaining variation in density-feedback strength across species, with the highest non-control, model-averaged effect sizes related to extreme precipitation variables. We could not link our results directly to other published studies, because ecologists use contrasting responses, predictors and statistical approaches to correlate density feedback and climate – at the expense of comparability in a macroecological context. Censuses of multiple populations within a given species, and a priori knowledge of the spatial scales at which density feedbacks interact with climate, seem to be necessary to determine cross-taxa variation in this phenomenon. Despite the availability of robust modelling tools, the

  7. Window area and development drive spatial variation in bird-window collisions in an urban landscape.

    Directory of Open Access Journals (Sweden)

    Stephen B Hager

    Full Text Available Collisions with windows are an important human-related threat to birds in urban landscapes. However, the proximate drivers of collisions are not well understood, and no study has examined spatial variation in mortality in an urban setting. We hypothesized that the number of fatalities at buildings varies with window area and habitat features that influence avian community structure. In 2010 we documented bird-window collisions (BWCs and characterized avian community structure at 20 buildings in an urban landscape in northwestern Illinois, USA. For each building and season, we conducted 21 daily surveys for carcasses and nine point count surveys to estimate relative abundance, richness, and diversity. Our sampling design was informed by experimentally estimated carcass persistence times and detection probabilities. We used linear and generalized linear mixed models to evaluate how habitat features influenced community structure and how mortality was affected by window area and factors that correlated with community structure. The most-supported model was consistent for all community indices and included effects of season, development, and distance to vegetated lots. BWCs were related positively to window area and negatively to development. We documented mortalities for 16/72 (22% species (34 total carcasses recorded at buildings, and BWCs were greater for juveniles than adults. Based on the most-supported model of BWCs, the median number of annual predicted fatalities at study buildings was 3 (range = 0-52. These results suggest that patchily distributed environmental resources and levels of window area in buildings create spatial variation in BWCs within and among urban areas. Current mortality estimates place little emphasis on spatial variation, which precludes a fundamental understanding of the issue. To focus conservation efforts, we illustrate how knowledge of the structural and environmental factors that influence bird

  8. Multiscale Tikhonov-Total Variation Image Restoration Using Spatially Varying Edge Coherence Exponent.

    Science.gov (United States)

    Prasath, V B Surya; Vorotnikov, Dmitry; Pelapur, Rengarajan; Jose, Shani; Seetharaman, Guna; Palaniappan, Kannappan

    2015-12-01

    Edge preserving regularization using partial differential equation (PDE)-based methods although extensively studied and widely used for image restoration, still have limitations in adapting to local structures. We propose a spatially adaptive multiscale variable exponent-based anisotropic variational PDE method that overcomes current shortcomings, such as over smoothing and staircasing artifacts, while still retaining and enhancing edge structures across scale. Our innovative model automatically balances between Tikhonov and total variation (TV) regularization effects using scene content information by incorporating a spatially varying edge coherence exponent map constructed using the eigenvalues of the filtered structure tensor. The multiscale exponent model we develop leads to a novel restoration method that preserves edges better and provides selective denoising without generating artifacts for both additive and multiplicative noise models. Mathematical analysis of our proposed method in variable exponent space establishes the existence of a minimizer and its properties. The discretization method we use satisfies the maximum-minimum principle which guarantees that artificial edge regions are not created. Extensive experimental results using synthetic, and natural images indicate that the proposed multiscale Tikhonov-TV (MTTV) and dynamical MTTV methods perform better than many contemporary denoising algorithms in terms of several metrics, including signal-to-noise ratio improvement and structure preservation. Promising extensions to handle multiplicative noise models and multichannel imagery are also discussed.

  9. Bayesian Spatial Modelling with R-INLA

    OpenAIRE

    Finn Lindgren; Håvard Rue

    2015-01-01

    The principles behind the interface to continuous domain spatial models in the R- INLA software package for R are described. The integrated nested Laplace approximation (INLA) approach proposed by Rue, Martino, and Chopin (2009) is a computationally effective alternative to MCMC for Bayesian inference. INLA is designed for latent Gaussian models, a very wide and flexible class of models ranging from (generalized) linear mixed to spatial and spatio-temporal models. Combined with the stochastic...

  10. Spatial Distribution of the Coefficient of Variation for the Paleo-Earthquakes in Japan

    Science.gov (United States)

    Nomura, S.; Ogata, Y.

    2015-12-01

    Renewal processes, point prccesses in which intervals between consecutive events are independently and identically distributed, are frequently used to describe this repeating earthquake mechanism and forecast the next earthquakes. However, one of the difficulties in applying recurrent earthquake models is the scarcity of the historical data. Most studied fault segments have few, or only one observed earthquake that often have poorly constrained historic and/or radiocarbon ages. The maximum likelihood estimate from such a small data set can have a large bias and error, which tends to yield high probability for the next event in a very short time span when the recurrence intervals have similar lengths. On the other hand, recurrence intervals at a fault depend on the long-term slip rate caused by the tectonic motion in average. In addition, recurrence times are also fluctuated by nearby earthquakes or fault activities which encourage or discourage surrounding seismicity. These factors have spatial trends due to the heterogeneity of tectonic motion and seismicity. Thus, this paper introduces a spatial structure on the key parameters of renewal processes for recurrent earthquakes and estimates it by using spatial statistics. Spatial variation of mean and variance parameters of recurrence times are estimated in Bayesian framework and the next earthquakes are forecasted by Bayesian predictive distributions. The proposal model is applied for recurrent earthquake catalog in Japan and its result is compared with the current forecast adopted by the Earthquake Research Committee of Japan.

  11. Effects of Spatial Variations in Packing Fraction on Reactor Physics Parameters in Pebble-Bed Reactors

    Energy Technology Data Exchange (ETDEWEB)

    William K. Terry; A. M. Ougouag; Farzad Rahnema; Michael Scott McKinley

    2003-04-01

    The well-known spatial variation of packing fraction near the outer boundary of a pebble-bed reactor core is cited. The ramifications of this variation are explored with the MCNP computer code. It is found that the variation has negligible effects on the global reactor physics parameters extracted from the MCNP calculations for use in analysis by diffusion-theory codes, but for local reaction rates the effects of the variation are naturally important. Included is some preliminary work in using first-order perturbation theory for estimating the effect of the spatial variation of packing fraction on the core eigenvalue and the fision density distribution.

  12. Investigating of spatial variations of PM2.5 concentration in Suzhou using remote sensing imagery

    Science.gov (United States)

    Zhang, Shanzheng; Li, Bailiang

    2017-04-01

    Suzhou is located at the center of Yangtze Delta, suffering the air pollution from construction of mega city, industrial emission and traffic development. Particulate matter not greater than 2.5 micrometers (PM2.5) is now considered as the most important pollutants in the air in East China. For Suzhou city, some studies on PM2.5 temporal variations based on ground measurements have been conducted. However, until now, there is limited remote sensing based research to investigate the spatial pattern of PM2.5 in Suzhou. MODIS is often used to evaluate the spatial variabiilty of air quality, however, due to its low spatial resolution (250m), we have adopted China launched HJ-1 satellite with 30 m resolution of CCD sensor. Following the solar radiation S6 model and dark object atmospheric correction method (Kaufman,et al., 2000), atmospheric optical depth (AOD) was estimated. A statistical relationship has been built up between AOD and PM2.5. We have retrieved the spatial distribution of PM2.5 across Suzhou city in the winter of 2014. Results indicate that PM2.5 has the highest value in Kunshan (East of Suzhou) and Changshu and Taicang (NE of Suzhou) due to the heavy-polluted industry, while in the island of the Taihu Lake, the PM2.5 is significantly lower than other places maybe because of high deposition rate of PM2.5 over water and forest surfaces. The spatial variation also shows that traffic has less contribution to the PM2.5 generation than the industry. We believe this study will be very useful to identify the causes of local PM2.5 pollution. The findings could also benefit local management and policy making.

  13. Evaluating spatial patterns in hydrological modelling

    DEFF Research Database (Denmark)

    Koch, Julian

    of spatial information in a holistic assessment. Opposed, statistical measures typically only address a limited amount of spatial information. A web-based survey and a citizen science project are employed to quantify the collective perceptive skills of humans aiming at benchmarking spatial metrics...... of environmental science, such as meteorology, geostatistics or geography. In total, seven metrics are evaluated with respect to their capability to quantitatively compare spatial patterns. The human visual perception is often considered superior to computer based measures, because it integrates various dimensions...... with respect to their capability to mimic human evaluations. This PhD thesis aims at expanding the standard toolbox of spatial model evaluation with innovative metrics that adequately compare spatial patterns. Driven by the rise of more complex model structures and the increase of suitable remote sensing...

  14. Spatial and sex-specific variation in growth of albacore tuna (Thunnus alalunga across the South Pacific Ocean.

    Directory of Open Access Journals (Sweden)

    Ashley J Williams

    Full Text Available Spatial variation in growth is a common feature of demersal fish populations which often exist as discrete adult sub-populations linked by a pelagic larval stage. However, it remains unclear whether variation in growth occurs at similar spatial scales for populations of highly migratory pelagic species, such as tuna. We examined spatial variation in growth of albacore Thunnus alalunga across 90° of longitude in the South Pacific Ocean from the east coast of Australia to the Pitcairn Islands. Using length-at-age data from a validated ageing method we found evidence for significant variation in length-at-age and growth parameters (L(∞ and k between sexes and across longitudes. Growth trajectories were similar between sexes up until four years of age, after which the length-at-age for males was, on average, greater than that for females. Males reached an average maximum size more than 8 cm larger than females. Length-at-age and growth parameters were consistently greater at more easterly longitudes than at westerly longitudes for both females and males. Our results provide strong evidence that finer spatial structure exists within the South Pacific albacore stock and raises the question of whether the scale of their "highly migratory" nature should be re-assessed. Future stock assessment models for South Pacific albacore should consider sex-specific growth curves and spatial variation in growth within the stock.

  15. Spatial Variation in Anaerobic Microbial Communities in Wetland Margin Soils

    Science.gov (United States)

    Rich, H.; Kannenberg, S.; Ludwig, S.; Nelson, L. C.; Spawn, S.; Porterfield, J.; Schade, J. D.

    2012-12-01

    Climate change is predicted to increase the severity and frequency of precipitation and drought events, which may result in substantial temporal variation in the size of wetlands. Wetlands are the world's largest natural emitter of methane, a greenhouse gas that is 20 times more effective at trapping heat than carbon dioxide. Changes in the dynamics of wetland size may lead to changes in the extent and timing of inundation of soils in ephemeral margins, which is likely to influence microbes that rely on anoxic conditions. The impact on process rates may depend on the structure of the community of microbes present in the soil, however, the link between microbial structure and patterns in process rates in soils is not well understood. Our goal was to use molecular techniques to compare microorganism communities in two wetlands that differ in the extent and duration of inundation of marginal soils to assess how these communities may change with changes in climate, and the potential consequences for methane production. This will allow us to examine how community composition changes with soil conditions such as moisture content, frequency of drought and abundance of available carbon. The main focus of this project was to determine the presence or absence of acetoclastic (AC) and hydrogenotrophic (HT) methanogens. AC methanogens use acetate as their main substrate, while HT methanogens use Hydrogen and Carbon dioxide. The relative proportion of these pathways depends on soil conditions, such as competition with other anaerobic microbes and the amount of labile carbon, and spatial patterns in the presence of each can give insight into the soil conditions of a wetland site. We sampled soil from three different wetland ponds of varying permanence in the St Olaf Natural Lands in Northfield, Minnesota, and extracted DNA from these soil samples with a MoBio PowerSoil DNA Isolation Kit. With PCR and seven different primer sets, we tested the extracted DNA for the presence of

  16. Spatial Bayesian hierarchical modelling of extreme sea states

    Science.gov (United States)

    Clancy, Colm; O'Sullivan, John; Sweeney, Conor; Dias, Frédéric; Parnell, Andrew C.

    2016-11-01

    A Bayesian hierarchical framework is used to model extreme sea states, incorporating a latent spatial process to more effectively capture the spatial variation of the extremes. The model is applied to a 34-year hindcast of significant wave height off the west coast of Ireland. The generalised Pareto distribution is fitted to declustered peaks over a threshold given by the 99.8th percentile of the data. Return levels of significant wave height are computed and compared against those from a model based on the commonly-used maximum likelihood inference method. The Bayesian spatial model produces smoother maps of return levels. Furthermore, this approach greatly reduces the uncertainty in the estimates, thus providing information on extremes which is more useful for practical applications.

  17. Hierarchical modeling and analysis for spatial data

    CERN Document Server

    Banerjee, Sudipto; Gelfand, Alan E

    2003-01-01

    Among the many uses of hierarchical modeling, their application to the statistical analysis of spatial and spatio-temporal data from areas such as epidemiology And environmental science has proven particularly fruitful. Yet to date, the few books that address the subject have been either too narrowly focused on specific aspects of spatial analysis, or written at a level often inaccessible to those lacking a strong background in mathematical statistics.Hierarchical Modeling and Analysis for Spatial Data is the first accessible, self-contained treatment of hierarchical methods, modeling, and dat

  18. Application of mobile sampling to investigate spatial variation in fine particle composition

    Science.gov (United States)

    Li, Hugh Z.; Dallmann, Timothy R.; Gu, Peishi; Presto, Albert A.

    2016-10-01

    Long-term exposure to particulate matter (PM) is a major contributor to air pollution related deaths. Evidence indicates that metals play an important role in harming human health due to their redox potential. We conducted a mobile sampling campaign in 2013 summer and winter in Pittsburgh, PA to characterize spatial variation in PM2.5 mass and composition. Thirty-six sites were chosen based on three stratification variables: traffic density, proximity to point sources, and elevation. We collected filters in three time sessions (morning, afternoon, and overnight) in each season. X-ray fluorescence (XRF) was used to analyze concentrations of 26 elements: Na, Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Zr, Cd, Sb, and Pb. Trace elements had a broad range of concentrations from 0 to 300 ng/m3. Comparison of data from mobile sampling filters with stationary monitors suggested that the mobile sampling strategy did not lead to a biased dataset. We developed Land Use Regression (LUR) models to describe spatial variation of PM2.5, Si, S, Cl, K, Ca, Ti, Cr, Fe, Cu, and Zn. Using ArcGIS-10.3 (ESRI, Redlands, CA), we extracted different independent variables related to traffic influence, land-use type, and facility emissions based on the National Emission Inventory (NEI). To validate LUR models, we used regression diagnostics such as leave-one-out cross validation (LOOCV), mean studentized prediction residual (MSPR), and root mean square of studentized residuals (RMS). The number of predictors in final LUR models ranged from 1 to 6. Models had an average R2 of 0.57 (SD = 0.16). Traffic related variables explained the most variability with an average R2 contribution of 0.20 (SD = 0.20). Overall, these results demonstrated significant intra-urban spatial variability of fine particle composition.

  19. Spectroscopic observations of spatial and temporal variations on Venus

    Science.gov (United States)

    Young, A. T.; Young, L. G.; Woszczyk, A.

    1974-01-01

    Details of the Table Mountain spectroscopic patrol of Venus in September-October 1972 are given. The data indicate systematic variation over the disc, with more CO2 absorption near the terminator than at the limb, and slightly more in the southern than in the northern hemisphere. The semiregular four-day variation, reported to occur simultaneously over the disk at 8689 A by Young et al. (1973), is confirmed by observations of the 7820 A and 7883 A CO2 bands.

  20. Spatial Variation of Arsenic in Soil, Irrigation Water, and Plant Parts: A Microlevel Study

    Science.gov (United States)

    Kabir, M. S.; Salam, M. A.; Paul, D. N. R.; Hossain, M. I.; Rahman, N. M. F.; Aziz, Abdullah

    2016-01-01

    Arsenic pollution became a great problem in the recent past in different countries including Bangladesh. The microlevel studies were conducted to see the spatial variation of arsenic in soils and plant parts contaminated through ground water irrigation. The study was performed in shallow tube well command areas in Sadar Upazila (subdistrict), Faridpur, Bangladesh, where both soil and irrigation water arsenic are high. Semivariogram models were computed to determine the spatial dependency of soil, water, grain, straw, and husk arsenic (As). An arsenic concentration surface was created spatially to describe the distribution of arsenic in soil, water, grain, straw, and husk. Command area map was digitized using Arcview GIS from the “mouza” map. Both arsenic contaminated irrigation water and the soils were responsible for accumulation of arsenic in rice straw, husk, and grain. The accumulation of arsenic was higher in water followed by soil, straw, husk, and grain. Arsenic concentration varied widely within command areas. The extent and propensity of arsenic concentration were higher in areas where high concentration of arsenic existed in groundwater and soils. Spherical model was a relatively better and appropriate model. Kriging method appeared to be more suitable in creating interpolated surface. The average arsenic content in grain was 0.08–0.45 mg/kg while in groundwater arsenic level it ranged from 138.0 to 191.3 ppb.

  1. Spatial and Temporal Variations of Surface Characteristics on the Greenland Ice Sheet as Derived from Passive Microwave Observations

    Science.gov (United States)

    Anderson, Mark; Rowe, Clinton; Kuivinen, Karl; Mote, Thomas

    1996-01-01

    The primary goals of this research were to identify and begin to comprehend the spatial and temporal variations in surface characteristics of the Greenland ice sheet using passive microwave observations, physically-based models of the snowpack and field observations of snowpack and firn properties.

  2. Attribution of spatial and temporal variations in terrestrial methane flux over North America

    Directory of Open Access Journals (Sweden)

    X. F. Xu

    2010-07-01

    Full Text Available The attribution of spatial and temporal variations in terrestrial methane (CH4 flux is essential for assessing and mitigating CH4 emission from terrestrial ecosystems. In this study, we used a process-based model, the Dynamic Land Ecosystem Model (DLEM, in conjunction with spatial data of six major environmental factors to attribute the spatial and temporal variations in the terrestrial methane (CH4 flux over North America from 1979 to 2008 to six individual factors and their interaction. Over the past three decades, our simulation indicates that global change factors accumulatively contributed 43.05 Tg CH4-C (1 Tg = 1012 g emission over North America, among which ozone (O3 pollution led to a reduced CH4 emission by 2.69 Tg CH4-C, all other factors including climate variability, nitrogen (N deposition, rising atmospheric carbon dioxide (CO2, N fertilization, and land conversion increased terrestrial CH4 emissions by 40.37 Tg CH4-C, 0.42 Tg CH4-C, 6.95 Tg CH4-C, 0.11 Tg CH4-C, and 3.70 Tg CH4-C, respectively, and interaction between/among these global change factors led to a decline of CH4 emission by 5.80 Tg CH4-C. Climatic variability dominated the inter-annual variations in terrestrial CH4 fluxes at both continental and country levels. The relative importance of each environmental factor in determining the magnitude of methane flux shows substantially spatial variation across North America. This factorial attribution of CH4 fluxes over the North America might benefit policy makers who would like to curb climate warming by reducing CH4 emission.

  3. Spatial-temporal characters of Antarctic sea ice variation

    Institute of Scientific and Technical Information of China (English)

    Ma Lijuan; Lu Longhua; Bian Lingen

    2004-01-01

    Using sea ice concentration dataset covering the period of 1968-2002 obtained from the Hadley Center of UK, this paper investigates characters of Antarctic sea ice variations .The finding demonstrates that the change of mean sea-ice extent is almost consistent with that of sea-ice area, so sea-ice extent can be chosen to go on this research. The maximum and the minimum of Antarctic sea ice appear in September and February respectively. The maximum and the maximal variation of sea ice appear in Weddell Sea and Ross Sea, while the minimum and the minimal variation of sea-ice appear in Antarctic Peninsula. In recent 35 years, as a whole, Antarctic sea ice decreased distinctly. Moreover, there are 5 subdivision characteristic regions considering their different variations. Hereinto, the sea-ice extent of Weddell Sea and Ross Sea regions extends and area increases, while the sea-ice extent of the other three regions contracts and area decreases. They are all of obvious 2-4 years and 5-7 years significant oscillation periods. It is of significance for further understanding the sea-ice-air interaction in Antarctica region and discussing the relationship between sea-ice variation and atmospheric circulation.

  4. Spatial Evolution of the Thickness Variations over a CFRP Laminated Structure

    Science.gov (United States)

    Davila, Yves; Crouzeix, Laurent; Douchin, Bernard; Collombet, Francis; Grunevald, Yves-Henri

    2017-01-01

    Ply thickness is one of the main drivers of the structural performance of a composite part. For stress analysis calculations (e.g., finite element analysis), composite plies are commonly considered to have a constant thickness compared to the reality (coefficients of variation up to 9% of the mean ply thickness). Unless this variability is taken into account reliable property predictions cannot be made. A modelling approach of such variations is proposed using parameters obtained from a 16-ply quasi-isotropic CFRP plate cured in an autoclave. A discrete Fourier transform algorithm is used to analyse the frequency response of the observed ply and plate thickness profiles. The model inputs, obtained by a mathematical representation of the ply thickness profiles, permit the generation of a representative stratification considering the spatial continuity of the thickness variations that are in good agreement with the real ply profiles spread over the composite part. A residual deformation FE model of the composite plate is used to illustrate the feasibility of the approach.

  5. Spatial variation in school performance, a local analysis of socio ...

    African Journals Online (AJOL)

    Setup

    Poor pass rates of matric learners at secondary schools in South Africa has been a concern for ... family or individual on a hierarchal social structure based on their access to, ... For a long time the complexities of spatial data ... Systems (GIS) has had an effect on quantitative geography and this ability to apply quantitative.

  6. Exploring the relationship between malaria, rainfall intermittency, and spatial variation in rainfall seasonality

    Science.gov (United States)

    Merkord, C. L.; Wimberly, M. C.; Henebry, G. M.; Senay, G. B.

    2014-12-01

    Malaria is a major public health problem throughout tropical regions of the world. Successful prevention and treatment of malaria requires an understanding of the environmental factors that affect the life cycle of both the malaria pathogens, protozoan parasites, and its vectors, anopheline mosquitos. Because the egg, larval, and pupal stages of mosquito development occur in aquatic habitats, information about the spatial and temporal distribution of rainfall is critical for modeling malaria risk. Potential sources of hydrological data include satellite-derived rainfall estimates (TRMM and GPM), evapotranspiration derived from a simplified surface energy balance, and estimates of soil moisture and fractional water cover from passive microwave imagery. Previous studies have found links between malaria cases and total monthly or weekly rainfall in areas where both are highly seasonal. However it is far from clear that monthly or weekly summaries are the best metrics to use to explain malaria outbreaks. It is possible that particular temporal or spatial patterns of rainfall result in better mosquito habitat and thus higher malaria risk. We used malaria case data from the Amhara region of Ethiopia and satellite-derived rainfall estimates to explore the relationship between malaria outbreaks and rainfall with the goal of identifying the most useful rainfall metrics for modeling malaria occurrence. First, we explored spatial variation in the seasonal patterns of both rainfall and malaria cases in Amhara. Second, we assessed the relative importance of different metrics of rainfall intermittency, including alternation of wet and dry spells, the strength of intensity fluctuations, and spatial variability in these measures, in determining the length and severity of malaria outbreaks. We also explored the sensitivity of our results to the choice of method for describing rainfall intermittency and the spatial and temporal scale at which metrics were calculated. Results

  7. On spatially explicit models of cholera epidemics

    National Research Council Canada - National Science Library

    Bertuzzo, E; Casagrandi, R; Gatto, M; Rodriguez-Iturbe, I; Rinaldo, A

    2010-01-01

    We generalize a recently proposed model for cholera epidemics that accounts for local communities of susceptibles and infectives in a spatially explicit arrangement of nodes linked by networks having...

  8. SIMULATION MODELING SLOW SPATIALLY HETER- OGENEOUS COAGULATION

    Directory of Open Access Journals (Sweden)

    P. A. Zdorovtsev

    2013-01-01

    Full Text Available A new model of spatially inhomogeneous coagulation, i.e. formation of larger clusters by joint interaction of smaller ones, is under study. The results of simulation are compared with known analytical and numerical solutions.

  9. Spatial averaging infiltration model for layered soil

    Institute of Scientific and Technical Information of China (English)

    HU HePing; YANG ZhiYong; TIAN FuQiang

    2009-01-01

    To quantify the influences of soil heterogeneity on infiltration, a spatial averaging infiltration model for layered soil (SAI model) is developed by coupling the spatial averaging approach proposed by Chen et al. and the Generalized Green-Ampt model proposed by Jia et al. In the SAI model, the spatial heterogeneity along the horizontal direction is described by a probability distribution function, while that along the vertical direction is represented by the layered soils. The SAI model is tested on a typical soil using Monte Carlo simulations as the base model. The results show that the SAI model can directly incorporate the influence of spatial heterogeneity on infiltration on the macro scale. It is also found that the homogeneous assumption of soil hydraulic conductivity along the horizontal direction will overestimate the infiltration rate, while that along the vertical direction will underestimate the infiltration rate significantly during rainstorm periods. The SAI model is adopted in the spatial averaging hydrological model developed by the authors, and the results prove that it can be applied in the macro-scale hydrological and land surface process modeling in a promising way.

  10. Spatial averaging infiltration model for layered soil

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    To quantify the influences of soil heterogeneity on infiltration, a spatial averaging infiltration model for layered soil (SAI model) is developed by coupling the spatial averaging approach proposed by Chen et al. and the Generalized Green-Ampt model proposed by Jia et al. In the SAI model, the spatial hetero- geneity along the horizontal direction is described by a probability distribution function, while that along the vertical direction is represented by the layered soils. The SAI model is tested on a typical soil using Monte Carlo simulations as the base model. The results show that the SAI model can directly incorporate the influence of spatial heterogeneity on infiltration on the macro scale. It is also found that the homogeneous assumption of soil hydraulic conductivity along the horizontal direction will overes- timate the infiltration rate, while that along the vertical direction will underestimate the infiltration rate significantly during rainstorm periods. The SAI model is adopted in the spatial averaging hydrological model developed by the authors, and the results prove that it can be applied in the macro-scale hy- drological and land surface process modeling in a promising way.

  11. Spatial occupancy models for large data sets

    Science.gov (United States)

    Johnson, Devin S.; Conn, Paul B.; Hooten, Mevin B.; Ray, Justina C.; Pond, Bruce A.

    2013-01-01

    Since its development, occupancy modeling has become a popular and useful tool for ecologists wishing to learn about the dynamics of species occurrence over time and space. Such models require presence–absence data to be collected at spatially indexed survey units. However, only recently have researchers recognized the need to correct for spatially induced overdisperison by explicitly accounting for spatial autocorrelation in occupancy probability. Previous efforts to incorporate such autocorrelation have largely focused on logit-normal formulations for occupancy, with spatial autocorrelation induced by a random effect within a hierarchical modeling framework. Although useful, computational time generally limits such an approach to relatively small data sets, and there are often problems with algorithm instability, yielding unsatisfactory results. Further, recent research has revealed a hidden form of multicollinearity in such applications, which may lead to parameter bias if not explicitly addressed. Combining several techniques, we present a unifying hierarchical spatial occupancy model specification that is particularly effective over large spatial extents. This approach employs a probit mixture framework for occupancy and can easily accommodate a reduced-dimensional spatial process to resolve issues with multicollinearity and spatial confounding while improving algorithm convergence. Using open-source software, we demonstrate this new model specification using a case study involving occupancy of caribou (Rangifer tarandus) over a set of 1080 survey units spanning a large contiguous region (108 000 km2) in northern Ontario, Canada. Overall, the combination of a more efficient specification and open-source software allows for a facile and stable implementation of spatial occupancy models for large data sets.

  12. Evaluating spatial patterns in hydrological modelling

    DEFF Research Database (Denmark)

    Koch, Julian

    is not fully exploited by current modelling frameworks due to the lack of suitable spatial performance metrics. Furthermore, the traditional model evaluation using discharge is found unsuitable to lay confidence on the predicted catchment inherent spatial variability of hydrological processes in a fully...... the contiguous United Sates (10^6 km2). To this end, the thesis at hand applies a set of spatial performance metrics on various hydrological variables, namely land-surface-temperature (LST), evapotranspiration (ET) and soil moisture. The inspiration for the applied metrics is found in related fields...

  13. Spatial and Temporal Variations in Arsenic Exposure via Drinking-water in Northern Argentina

    National Research Council Canada - National Science Library

    Gabriela Concha; Barbro Nermell; Marie Vahter

    2006-01-01

    This study evaluated the spatial, temporal and inter-individual variations in exposure to arsenic via drinking-water in Northern Argentina, based on measurements of arsenic in water, urine, and hair...

  14. Measurement Models of Forest Biodiversity Variation and Its Controlling Study in China

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    According to the evaluative data of forest biodiversity variation in China from 1973 to 1998, not only the gray model GM( 1,2), but also the status spatial characterization model with the optimal control model for forest biodiversity variation is developed by using some mathematic approaches and knowledge in economic cybernetics. Furthermore, the structural characteristics of forest biodiversity variation are analyzed. The paper points out that the variation of forest biodiversity is instable, but it ca...

  15. Can spatial statistical river temperature models be transferred between catchments?

    Science.gov (United States)

    Jackson, Faye L.; Fryer, Robert J.; Hannah, David M.; Malcolm, Iain A.

    2017-09-01

    There has been increasing use of spatial statistical models to understand and predict river temperature (Tw) from landscape covariates. However, it is not financially or logistically feasible to monitor all rivers and the transferability of such models has not been explored. This paper uses Tw data from four river catchments collected in August 2015 to assess how well spatial regression models predict the maximum 7-day rolling mean of daily maximum Tw (Twmax) within and between catchments. Models were fitted for each catchment separately using (1) landscape covariates only (LS models) and (2) landscape covariates and an air temperature (Ta) metric (LS_Ta models). All the LS models included upstream catchment area and three included a river network smoother (RNS) that accounted for unexplained spatial structure. The LS models transferred reasonably to other catchments, at least when predicting relative levels of Twmax. However, the predictions were biased when mean Twmax differed between catchments. The RNS was needed to characterise and predict finer-scale spatially correlated variation. Because the RNS was unique to each catchment and thus non-transferable, predictions were better within catchments than between catchments. A single model fitted to all catchments found no interactions between the landscape covariates and catchment, suggesting that the landscape relationships were transferable. The LS_Ta models transferred less well, with particularly poor performance when the relationship with the Ta metric was physically implausible or required extrapolation outside the range of the data. A single model fitted to all catchments found catchment-specific relationships between Twmax and the Ta metric, indicating that the Ta metric was not transferable. These findings improve our understanding of the transferability of spatial statistical river temperature models and provide a foundation for developing new approaches for predicting Tw at unmonitored locations across

  16. Confounding effects of spatial variation on shifts in phenology.

    Science.gov (United States)

    de Keyzer, Charlotte W; Rafferty, Nicole E; Inouye, David W; Thomson, James D

    2017-05-01

    Shifts in the timing of life history events have become an important source of information about how organisms are responding to climate change. Phenological data have generally been treated as purely temporal, with scant attention to the inherent spatial aspects of such data. However, phenological data are tied to a specific location, and considerations of sampling design, both over space and through time, can critically affect the patterns that emerge. Focusing on flowering phenology, we describe how purely spatial shifts, such as adding new study plots, or the colonization of a study plot by a new species, can masquerade as temporal shifts. Such shifts can look like responses to climate change but are not. Furthermore, the same aggregate phenological curves can be composed of individuals with either very different or very similar phenologies. We conclude with a set of recommendations to avoid ambiguities arising from the spatiotemporal duality of phenological data.

  17. Temporal and spatial variations of the Vienna aerosol.

    Science.gov (United States)

    Horvath, H; Habenreich, T A; Kreiner, I; Norek, C

    1989-07-01

    For several intensive sampling periods the mass concentration, light extinction, light scattering and light absorption coefficients, and the mass size distribution of the aerosol have been determined at up to eleven location in the non-industrial town of Vienna. Obviously, large variations of the measured values have been found. The following factors influenced the aerosol markedly: wind speed, wind direction, increased aerosol production such as by space heating or traffic and resuspension. Most of the variations in aerosol were found to be caused by these factors. A comparison of the mass concentration and light absorption of the aerosol upwind and downwind of Vienna permitted the estimation of locally produced aerosols: about 50% of the mass of the aerosol and 75% of the light-absorbing aerosol appears to be produced locally.

  18. Performance of Information Criteria for Spatial Models.

    Science.gov (United States)

    Lee, Hyeyoung; Ghosh, Sujit K

    2009-01-01

    Model choice is one of the most crucial aspect in any statistical data analysis. It is well known that most models are just an approximation to the true data generating process but among such model approximations it is our goal to select the "best" one. Researchers typically consider a finite number of plausible models in statistical applications and the related statistical inference depends on the chosen model. Hence model comparison is required to identify the "best" model among several such candidate models. This article considers the problem of model selection for spatial data. The issue of model selection for spatial models has been addressed in the literature by the use of traditional information criteria based methods, even though such criteria have been developed based on the assumption of independent observations. We evaluate the performance of some of the popular model selection critera via Monte Carlo simulation experiments using small to moderate samples. In particular, we compare the performance of some of the most popular information criteria such as Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), and Corrected AIC (AICc) in selecting the true model. The ability of these criteria to select the correct model is evaluated under several scenarios. This comparison is made using various spatial covariance models ranging from stationary isotropic to nonstationary models.

  19. Relevant Spatial Scales of Chemical Variation in Aplysina aerophoba

    Directory of Open Access Journals (Sweden)

    Oriol Sacristan-Soriano

    2011-11-01

    Full Text Available Understanding the scale at which natural products vary the most is critical because it sheds light on the type of factors that regulate their production. The sponge Aplysina aerophoba is a common Mediterranean sponge inhabiting shallow waters in the Mediterranean and its area of influence in Atlantic Ocean. This species contains large concentrations of brominated alkaloids (BAs that play a number of ecological roles in nature. Our research investigates the ecological variation in BAs of A. aerophoba from a scale of hundred of meters to thousand kilometers. We used a nested design to sample sponges from two geographically distinct regions (Canary Islands and Mediterranean, over 2500 km, with two zones within each region (less than 50 km, two locations within each zone (less than 5 km, and two sites within each location (less than 500 m. We used high-performance liquid chromatography to quantify multiple BAs and a spectrophotometer to quantify chlorophyll a (Chl a. Our results show a striking degree of variation in both natural products and Chl a content. Significant variation in Chl a content occurred at the largest and smallest geographic scales. The variation patterns of BAs also occurred at the largest and smallest scales, but varied depending on which BA was analyzed. Concentrations of Chl a and isofistularin-3 were negatively correlated, suggesting that symbionts may impact the concentration of some of these compounds. Our results underline the complex control of the production of secondary metabolites, with factors acting at both small and large geographic scales affecting the production of multiple secondary metabolites.

  20. Spatial and seasonal variations of the contamination within water body of the Grand Canal, China

    NARCIS (Netherlands)

    Wang, X.L.; Han, Jingyi; Xu, L.G.; Zhang, Q.

    2010-01-01

    To delineate the character of contaminations in the Grand Canal, China, a three-year study (2004-2006) was conducted to investigate variations the water quality in the canal. Results showed that the variation of water quality within the Grand Canal was of there is remarkable spatial and seasonal het

  1. Uncertainty in spatially explicit animal dispersal models

    Science.gov (United States)

    Mooij, Wolf M.; DeAngelis, Donald L.

    2003-01-01

    Uncertainty in estimates of survival of dispersing animals is a vexing difficulty in conservation biology. The current notion is that this uncertainty decreases the usefulness of spatially explicit population models in particular. We examined this problem by comparing dispersal models of three levels of complexity: (1) an event-based binomial model that considers only the occurrence of mortality or arrival, (2) a temporally explicit exponential model that employs mortality and arrival rates, and (3) a spatially explicit grid-walk model that simulates the movement of animals through an artificial landscape. Each model was fitted to the same set of field data. A first objective of the paper is to illustrate how the maximum-likelihood method can be used in all three cases to estimate the means and confidence limits for the relevant model parameters, given a particular set of data on dispersal survival. Using this framework we show that the structure of the uncertainty for all three models is strikingly similar. In fact, the results of our unified approach imply that spatially explicit dispersal models, which take advantage of information on landscape details, suffer less from uncertainly than do simpler models. Moreover, we show that the proposed strategy of model development safeguards one from error propagation in these more complex models. Finally, our approach shows that all models related to animal dispersal, ranging from simple to complex, can be related in a hierarchical fashion, so that the various approaches to modeling such dispersal can be viewed from a unified perspective.

  2. Models of Solar Irradiance Variations: Current Status

    Indian Academy of Sciences (India)

    Natalie A. Krivova; Sami K. Solanki

    2008-03-01

    Regular monitoring of solar irradiance has been carried out since 1978 to show that solar total and spectral irradiance varies at different time scales. Whereas variations on time scales of minutes to hours are due to solar oscillations and granulation, variations on longer time scales are driven by the evolution of the solar surface magnetic field. Here the most recent advances in modelling of solar irradiance variations on time scales longer than a day are briefly reviewed.

  3. Spatial interactions in agent-based modeling

    CERN Document Server

    Ausloos, Marcel; Merlone, Ugo

    2014-01-01

    Agent Based Modeling (ABM) has become a widespread approach to model complex interactions. In this chapter after briefly summarizing some features of ABM the different approaches in modeling spatial interactions are discussed. It is stressed that agents can interact either indirectly through a shared environment and/or directly with each other. In such an approach, higher-order variables such as commodity prices, population dynamics or even institutions, are not exogenously specified but instead are seen as the results of interactions. It is highlighted in the chapter that the understanding of patterns emerging from such spatial interaction between agents is a key problem as much as their description through analytical or simulation means. The chapter reviews different approaches for modeling agents' behavior, taking into account either explicit spatial (lattice based) structures or networks. Some emphasis is placed on recent ABM as applied to the description of the dynamics of the geographical distribution o...

  4. Spatial and temporal variations in glacier hydrology on Storglaciaeren, Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Peter (Dept. of Physical Geography and Quaternary Geology, Stockholm Univ., Stockholm (Sweden)); Naeslund, Jens-Ove (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2009-06-15

    The aim of the current research project was to provide a framework of real conditions within which to interpret theory and extrapolate likely conditions beneath a future ice sheet over Fennoscandia. The purpose of this report is to summarize the experimental work on glacier hydrology and basal hydraulic conditions performed on Storglaciaeren, northern Sweden, during the years 1990-2006. Surface fed subglacial hydrological systems are extremely dynamic because the input rates of rain and temperature-controlled surface melt fluctuate, and the geometry of flow paths is constantly changing due to ice deformation which tends to open and close the flow paths. The hydrological system of a glacier is quite unusual because since liquid water flows through conduits made of its solid phase (ice). Understanding the expected dynamic range of a glacier's hydrological system is best studied by in situ measurements. The processes studied on Storglaciaeren can be expected to apply to ice sheet scale, albeit on different spatial scales. Since Storglaciaeren is a polythermal glacier with a large fraction of ice below freezing and at the melting point and with a surface-fed hydrological system of conduits and tunnels, results apply to the lower elevation regions where the surface is composed of ice (ablation zone) rather than composed of snow (accumulation zone) found at higher elevations of the glaciers and ice sheets, Therefore, our results apply to the ablation zone of the past Fennoscandian Ice Sheet. In this report we discuss the measurements made to assess the subglacial conditions that provide a potential analogue for conditions under the Fennoscandian Ice Sheet. For this purpose field work was performed on from 2003 to 2006 yielding subglacial water pressure measurements. We have included a large quantity of unpublished data from Storglaciaeren from different research projects conducted since 1990. Together these data provide a picture of the temporal and spatial water

  5. Spatial and spatiotemporal variation in metapopulation structure affects population dynamics in a passively dispersing arthropod.

    Science.gov (United States)

    De Roissart, Annelies; Wang, Shaopeng; Bonte, Dries

    2015-11-01

    The spatial and temporal variation in the availability of suitable habitat within metapopulations determines colonization-extinction events, regulates local population sizes and eventually affects local population and metapopulation stability. Insights into the impact of such a spatiotemporal variation on the local population and metapopulation dynamics are principally derived from classical metapopulation theory and have not been experimentally validated. By manipulating spatial structure in artificial metapopulations of the spider mite Tetranychus urticae, we test to which degree spatial (mainland-island metapopulations) and spatiotemporal variation (classical metapopulations) in habitat availability affects the dynamics of the metapopulations relative to systems where habitat is constantly available in time and space (patchy metapopulations). Our experiment demonstrates that (i) spatial variation in habitat availability decreases variance in metapopulation size and decreases density-dependent dispersal at the metapopulation level, while (ii) spatiotemporal variation in habitat availability increases patch extinction rates, decreases local population and metapopulation sizes and decreases density dependence in population growth rates. We found dispersal to be negatively density dependent and overall low in the spatial variable mainland-island metapopulation. This demographic variation subsequently impacts local and regional population dynamics and determines patterns of metapopulation stability. Both local and metapopulation-level variabilities are minimized in mainland-island metapopulations relative to classical and patchy ones.

  6. Regulation mechanisms in spatial stochastic development models

    CERN Document Server

    Finkelshtein, Dmitri

    2008-01-01

    The aim of this paper is to analyze different regulation mechanisms in spatial continuous stochastic development models. We describe the density behavior for models with global mortality and local establishment rates. We prove that the local self-regulation via a competition mechanism (density dependent mortality) may suppress a unbounded growth of the averaged density if the competition kernel is superstable.

  7. Uncertainty in spatially explicit animal dispersal models

    NARCIS (Netherlands)

    Mooij, W.M.; DeAngelis, D.L.

    2003-01-01

    Uncertainty in estimates of survival of dispersing animals is a vexing difficulty in conservation biology. The current notion is that this uncertainty decreases the usefulness of spatially explicit population models in particular. We examined this problem by comparing dispersal models of three level

  8. Integrated statistical modelling of spatial landslide probability

    Science.gov (United States)

    Mergili, M.; Chu, H.-J.

    2015-09-01

    Statistical methods are commonly employed to estimate spatial probabilities of landslide release at the catchment or regional scale. Travel distances and impact areas are often computed by means of conceptual mass point models. The present work introduces a fully automated procedure extending and combining both concepts to compute an integrated spatial landslide probability: (i) the landslide inventory is subset into release and deposition zones. (ii) We employ a simple statistical approach to estimate the pixel-based landslide release probability. (iii) We use the cumulative probability density function of the angle of reach of the observed landslide pixels to assign an impact probability to each pixel. (iv) We introduce the zonal probability i.e. the spatial probability that at least one landslide pixel occurs within a zone of defined size. We quantify this relationship by a set of empirical curves. (v) The integrated spatial landslide probability is defined as the maximum of the release probability and the product of the impact probability and the zonal release probability relevant for each pixel. We demonstrate the approach with a 637 km2 study area in southern Taiwan, using an inventory of 1399 landslides triggered by the typhoon Morakot in 2009. We observe that (i) the average integrated spatial landslide probability over the entire study area corresponds reasonably well to the fraction of the observed landside area; (ii) the model performs moderately well in predicting the observed spatial landslide distribution; (iii) the size of the release zone (or any other zone of spatial aggregation) influences the integrated spatial landslide probability to a much higher degree than the pixel-based release probability; (iv) removing the largest landslides from the analysis leads to an enhanced model performance.

  9. Spatial and seasonal variations of leaf area index (LAI) in subtropical secondary forests related to floristic composition and stand characters

    Science.gov (United States)

    Zhu, Wenjuan; Xiang, Wenhua; Pan, Qiong; Zeng, Yelin; Ouyang, Shuai; Lei, Pifeng; Deng, Xiangwen; Fang, Xi; Peng, Changhui

    2016-07-01

    Leaf area index (LAI) is an important parameter related to carbon, water, and energy exchange between canopy and atmosphere and is widely applied in process models that simulate production and hydrological cycles in forest ecosystems. However, fine-scale spatial heterogeneity of LAI and its controlling factors have yet to be fully understood in Chinese subtropical forests. We used hemispherical photography to measure LAI values in three subtropical forests (Pinus massoniana-Lithocarpus glaber coniferous and evergreen broadleaved mixed forests, Choerospondias axillaris deciduous broadleaved forests, and L. glaber-Cyclobalanopsis glauca evergreen broadleaved forests) from April 2014 to January 2015. Spatial heterogeneity of LAI and its controlling factors were analysed using geostatistical methods and the generalised additive models (GAMs) respectively. Our results showed that LAI values differed greatly in the three forests and their seasonal variations were consistent with plant phenology. LAI values exhibited strong spatial autocorrelation for the three forests measured in January and for the L. glaber-C. glauca forest in April, July, and October. Obvious patch distribution pattern of LAI values occurred in three forests during the non-growing period and this pattern gradually dwindled in the growing season. Stem number, crown coverage, proportion of evergreen conifer species on basal area basis, proportion of deciduous species on basal area basis, and forest types affected the spatial variations in LAI values in January, while stem number and proportion of deciduous species on basal area basis affected the spatial variations in LAI values in July. Floristic composition, spatial heterogeneity, and seasonal variations should be considered for sampling strategy in indirect LAI measurement and application of LAI to simulate functional processes in subtropical forests.

  10. Spatial variations in δ13C and δ15N values of primary consumers in a coastal lagoon

    Science.gov (United States)

    Como, S.; Magni, P.; Van Der Velde, G.; Blok, F. S.; Van De Steeg, M. F. M.

    2012-12-01

    The analysis of the contribution of a food source to a consumer's diet or the trophic position of a consumer is highly sensitive to the variability of the isotopic values used as input data. However, little is known in coastal lagoons about the spatial variations in the isotopic values of primary consumers considered 'end members' in the isotope mixing models for quantifying the diet of secondary consumers or as a baseline for estimating the trophic position of consumers higher up in the food web. We studied the spatial variations in the δ13C and δ15N values of primary consumers and sedimentary organic matter (SOM) within a selected area of the Cabras lagoon (Sardinia, Italy). Our aim was to assess how much of the spatial variation in isotopic values of primary consumers was due to the spatial variability between sites and how much was due to differences in short distances from the shore. Samples were collected at four stations (50-100 m apart) selected randomly at two sites (1.5-2 km apart) chosen randomly at two distances from the shore (i.e. in proximity of the shore -Nearshore - and about 200 m away from the shore -Offshore). The sampling was repeated in March, May and August 2006 using new sites at the two chosen distances from the shore on each date. The isotopic values of size-fractionated seston and macrophytes were also analyzed as a complementary characterization of the study area. While δ15N did not show any spatial variations, the δ13C values of deposit feeders, Alitta (=Neanthes) succinea, Lekanesphaera hookeri, Hydrobia acuta and Gammarus aequicauda, were more depleted Offshore than Nearshore. For these species, there were significant effects of distance or distance × dates in the mean δ13C values, irrespective of the intrinsic variation between sites. SOM showed similar spatial variations in δ13C values, with Nearshore-Offshore differences up to 6‰. This indicates that the spatial isotopic changes are transferred from the food sources to the

  11. Spatial variation in adult sex ratio across multiple scales in the invasive golden apple snail, Pomacea canaliculata.

    Science.gov (United States)

    Xu, Meng; Fang, Miao; Yang, Yexin; Dick, Jaimie T A; Song, Hongmei; Luo, Du; Mu, Xidong; Gu, Dangen; Luo, Jianren; Hu, Yinchang

    2016-04-01

    Adult sex ratio (ASR) has critical effects on behavior and life history and has implications for population demography, including the invasiveness of introduced species. ASR exhibits immense variation in nature, yet the scale dependence of this variation is rarely analyzed. In this study, using the generalized multilevel models, we investigated the variation in ASR across multiple nested spatial scales and analyzed the underlying causes for an invasive species, the golden apple snail Pomacea canaliculata. We partitioned the variance in ASR to describe the variations at different scales and then included the explanatory variables at the individual and group levels to analyze the potential causes driving the variation in ASR. We firstly determined there is a significant female-biased ASR for this species when accounting for the spatial and temporal autocorrelations of sampling. We found that, counter to nearly equal distributed variation at plot, habitat and region levels, ASR showed little variation at the town level. Temperature and precipitation at the region level were significantly positively associated with ASR, whereas the individual weight, the density characteristic, and sampling time were not significant factors influencing ASR. Our study suggests that offspring sex ratio of this species may shape the general pattern of ASR in the population level while the environmental variables at the region level translate the unbiased offspring sex ratio to the female-biased ASR. Future research should consider the implications of climate warming on the female-biased ASR of this invasive species and thus on invasion pattern.

  12. Spatial variation of butyltins in an intermittent French River

    Science.gov (United States)

    Chahinian, N.; Bancon-Montigny, C.; Brunel, V.; Tournoud, M. G.

    2009-04-01

    Organotins (OTs) have been increasingly used in industrial applications because of their thermoresistant and biocidal properties: in the 1970s and 1980s Tributyltin (TBT) based anti-fouling paints were used on ships and vessels of all kinds. However, studies pointed out the highly toxic nature of these compounds and their active role as an endoctrine perturbator. This lead the EU to ban the use of TBT paints in 2003. The toxicity of OTs combined to their widespread use has lead then to be included in the priority list of the EU water framework directive. Organotins are prone to adsorption, can bond easily to particulate matter and "migrate" from the water column unto the sediments where their half-life can extend to a few decades. Consequently sediments can become important organotin stores and release OT compounds during dredging operations, storms, tides or floods. The main objective of this work was to investigate the presence of organotin compounds in the sediments and water column of an intermittent river reach i.e. to establish the presence of organotins in regular flow conditions and assess their spatial variability. The study zone is a reach of the Vène River located in southern France. The Vène is a major tributary of the Thau lagoon which is an important shellfish farming site and thus very vulnerable to OT contamination. Butyltin, trace metal and dissolved organic carbon (DOC) concentrations were measured on water and sediment samples collected over a 3 month period stretching from March to May 2008. The results revealed the presence of butyltins at concentrations exceeding the EU and French pollution limits. In terms of spatial variability, by combining the butyltin and the trace metal results at 16 locations along the reach, two point pollutions spots were identified, namely a sewage treatment plant and a drainage ditch. However, the later are not the only OT input sources, the results of the sediment analysis pointed out to a diffuse pollution

  13. Analysing earthquake slip models with the spatial prediction comparison test

    KAUST Repository

    Zhang, L.

    2014-11-10

    Earthquake rupture models inferred from inversions of geophysical and/or geodetic data exhibit remarkable variability due to uncertainties in modelling assumptions, the use of different inversion algorithms, or variations in data selection and data processing. A robust statistical comparison of different rupture models obtained for a single earthquake is needed to quantify the intra-event variability, both for benchmark exercises and for real earthquakes. The same approach may be useful to characterize (dis-)similarities in events that are typically grouped into a common class of events (e.g. moderate-size crustal strike-slip earthquakes or tsunamigenic large subduction earthquakes). For this purpose, we examine the performance of the spatial prediction comparison test (SPCT), a statistical test developed to compare spatial (random) fields by means of a chosen loss function that describes an error relation between a 2-D field (‘model’) and a reference model. We implement and calibrate the SPCT approach for a suite of synthetic 2-D slip distributions, generated as spatial random fields with various characteristics, and then apply the method to results of a benchmark inversion exercise with known solution. We find the SPCT to be sensitive to different spatial correlations lengths, and different heterogeneity levels of the slip distributions. The SPCT approach proves to be a simple and effective tool for ranking the slip models with respect to a reference model.

  14. Spatial and temporal variations of manganese concentrations in drinking water.

    Science.gov (United States)

    Barbeau, Benoit; Carrière, Annie; Bouchard, Maryse F

    2011-01-01

    The objective of this study was to assess the variability of manganese concentrations in drinking water (daily, seasonal, spatial) for eight communities who participated in an epidemiological study on neurotoxic effects associated with exposure to manganese in drinking water. We also assessed the performance of residential point-of-use and point-of-entry devices (POE) for reducing manganese concentrations in water. While the total Mn concentrations measured during this study were highly variable depending on the location (manganese concentration for 4 out of 5 sampling locations. The efficiency of reverse osmosis and ion exchange for total Mn removal was consistently high while activated carbon provided variable results. The four POE greensand filters investigated all increased (29 to 199%) manganese concentration, indicating deficient operation and/or maintenance practices. Manganese concentrations in the distribution system were equal or lower than at the inlet, indicating that sampling at the inlet of the distribution system is conservative. The decline in total Mn concentration was linked to higher water residence time in the distribution system.

  15. Modeling Per Capita State Health Expenditure Variat...

    Data.gov (United States)

    U.S. Department of Health & Human Services — Modeling Per Capita State Health Expenditure Variation State-Level Characteristics Matter, published in Volume 3, Issue 4, of the Medicare and Medicaid Research...

  16. Spatial-temporal variation of glacier over koshi basin, Himalaya

    Science.gov (United States)

    Gao, Y.; Yang, X.; Yao, T.

    2011-12-01

    Glacial change is a sensitive indicator of climate change and glacier meltwaters are vital water resource for more than 1/6 people in South and Central Asia. Due to the large extent and difficult accessibility of high mountainous terrain, there are few ground-based glacial observations. In the last decade, multi-temporal satellite imagery and older aerial photography have been used extensively to quantify glacier parameters such as glacier area, length, elevation, hypsography, and ice volume in mountainous areas throughout the world. In this study, a glacier inventory for Koshi Basin was generated for the year 1976, 1992, 2000 and 2009 using automated interpretation with remote sensing, GIS techniques and manual adjustments based on topographic maps, Landsat TM/ETM+, and SRTM DEM data. The area change of about ~3,407km2 was identified. During the past two decades, the average retreat rate of these glaciers was ~5.8% while the retreat rate from 2000 to 2009 was ~14.23%. Moreover, heavily debris-covered glaciers exist in this region. Some of them even extend several kilometers upstream from their terminus such as Kong Bu Re Bu Sang glacier. From 1992 to 2000, the decrease in total glacier area is ~30km2 while the debris coverage increased ~20km2. These increases generally occur near the boundary between clean ice and debris-covered glacier, while the glacial fronts are remarkably stable. In order to identify the effect of debris-covered glaciers, the variations of glacier area, length and elevation were calculated with and without debris-covered glaciers, respectively. Results show although the terminuses of glacial front were stagnant, the increase in debris-covered glacier contributes to the clean ice's length decrease and elevation increase, and thereby affects glacier's response to climate change. So we suggest that in the area where debris-covered glaciers are common, the clean ice and debris-covered area should be separated and the debris-covered part should

  17. On the temporal and spatial variation of ozone in Cyprus.

    Science.gov (United States)

    Kleanthous, Savvas; Vrekoussis, Mihalis; Mihalopoulos, Nikolaos; Kalabokas, Pavlos; Lelieveld, Jos

    2014-04-01

    More than sixteen years (1997-2013) of continuous ozone concentrations at the rural Agia Marina (EMEP, 532 ma.s.l.) station in Cyprus, together with a number of ancillary chemical and meteorological parameters have been analyzed on a multiannual, annual and diurnal basis. The observations reveal a) the presence of a prominent seasonality with maxima observed during summer (54±5 ppbv) and the minima in winter (39±3 ppbv) b) a relatively small diurnal variability with the noon levels (50±9 ppbv) being higher by ~4 pbbv compared to nighttime (46±9 ppbv) and c) a non-significant upward trend over the 16 years of 0.11±0.12 ppbv y(-1). To assess the spatial variability over Cyprus, simultaneous measurements in 2011-2012 have been performed at Inia, Stavrovouni and Cavo Greco, three remote marine monitoring sites located to the west, central and the east of the Island, respectively. Our results show that ambient ozone levels over Cyprus are mostly influenced by regional/transported ozone while the local precursor emissions play a minor role in ozone formation. On an annual basis a net ozone reduction of 1.5 and 1.0 ppbv occurs when the air masses originate from northerly and westerly directions, respectively, while this is 2.4 ppbv during southerly wind. This suggests continuous net ozone loss controlled by surface deposition and photochemical destruction, and highlights the importance of long-range transport in controlling ozone levels in Cyprus.

  18. Effect of assessment scale on spatial and temporal variations in CH4, C02, and N20 fluxes in a forested wetland

    Science.gov (United States)

    Zhaohua Dai; Carl Trettin; Changsheng Li; Harbin Li; Ge Sun; Devendra Amatya

    2011-01-01

    Emissions of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from a forested watershed (160 ha) in South Carolina, USA, were estimated with a spatially explicit watershed-scale modeling framework that utilizes the spatial variations in physical and biogeochemical characteristics across watersheds. The target watershed (WS80) consisting of wetland (23%) and...

  19. Coastal zone simulations with variational Boussinesq modelling

    NARCIS (Netherlands)

    Adytia, Didit

    2012-01-01

    The main challenge in deriving a Boussinesq model for water wave is to model accurately the dispersion and nonlinearity of waves. The dispersion is a depth-dependent relation between the wave speed and the wavelength. A Boussinesq-type model can be derived from the so-called variational principle

  20. Spatial variations of mercury in sediment of Minamata Bay, Japan.

    Science.gov (United States)

    Tomiyasu, Takashi; Matsuyama, Akito; Eguchi, Tomomi; Fuchigami, Yoko; Oki, Kimihiko; Horvat, Milena; Rajar, Rudi; Akagi, Hirokatsu

    2006-09-01

    Mercury-contaminated effluent was discharged into Minamata Bay from a chemical plant over a period of approximately 40 years until 1968. In October 1977, the Minamata Bay Pollution Prevention Project was initiated to dispose of sedimentary sludge containing mercury concentrations higher than 25 mg kg(-1). In March 1990, the project was completed. In an effort to estimate current contamination in the bay, the vertical and horizontal distributions of mercury in sediment were investigated. Sediment core samples were collected on June 26, 2002 at 16 locations in Minamata Bay and Fukuro Bay located in the southern part of Minamata Bay. The sediment in Fukuro Bay had not been dredged. The total mercury concentration in surface sediment was 1.4-4.3 mg kg(-1) (2.9+/-0.9 mg kg(-1), n=9) for the dredged area of Minamata Bay and 0.3-4.8 mg kg(-1) (3.6+/-1.6 mg kg(-1), n=4) for Fukuro Bay. In the lower layers of long cores taken from both areas, the total mercury concentration decreased with depth and finally showed relatively uniform low values. These values can be considered to represent the background concentration absent of anthropogenic influence, which was estimated for the study area to be 0.068+/-0.012 mg kg(-1) (n=10). From the surface, the total mercury concentration in Fukuro Bay increased with depth and reached a maximum at 8-14 cm. In Minamata Bay, several centimeters from the surface the total mercury concentration did not change significantly having considerably higher values than the background level. At six stations, the methylmercury concentration was determined. Although the vertical variations were similar to those for total mercury, Fukuro Bay sediment showed a higher concentration of methylmercury than Minamata Bay sediment.

  1. Stochastic spatial models of plant diseases

    CERN Document Server

    Brown, D H

    2001-01-01

    I present three models of plant--pathogen interactions. The models are stochastic and spatially explicit at the scale of individual plants. For each model, I use a version of pair approximation or moment closure along with a separation of timescales argument to determine the effects of spatial clustering on threshold structure. By computing the spatial structure early in an invasion, I find explicit corrections to mean field theory. In the first chapter, I present a lattice model of a disease that is not directly lethal to its host, but affects its ability to compete with neighbors. I use a type of pair approximation to determine conditions for invasions and coexistence. In the second chapter, I study a basic SIR epidemic point process in continuous space. I implement a multiplicative moment closure scheme to compute the threshold transmission rate as a function of spatial parameters. In the final chapter, I model the evolution of pathogen resistance when two plant species share a pathogen. Evolution may lead...

  2. Variation in spatial language and cognition: exploring visuo-spatial thinking and speaking cross-linguistically.

    Science.gov (United States)

    Soroli, Efstathia

    2012-08-01

    Languages differ strikingly in how they encode spatial information. This variability is realized with spatial semantic elements mapped across languages in very different ways onto lexical/syntactic structures. For example, satellite-framed languages (e.g., English) express MANNER: in the verb and PATH: in satellites, while verb-framed languages (e.g., French) lexicalize PATH: in the verb, leaving MANNER: implicit or peripheral. Some languages are harder to classify into these categories, rather presenting equipollently framed systems, such as Chinese (serial-verb constructions) or Greek (parallel verb- and satellite-framed structures in equally frequent contexts). Such properties seem to have implications not only on the formulation/articulation levels, but also on the conceptualization level, thereby reviving questions concerning the language-thought interface. The present study investigates the relative impact of language-independent and language-specific factors on spatial representations across three typologically different languages (English-French-Greek) combining a variety of complementary tasks (production, non-verbal, and verbal categorization). The findings show that typological properties of languages can have an impact on both linguistic and non-linguistic organization of spatial information, open new perspectives for the investigation of conceptualization, and contribute more generally to the debate concerning the universal and language-specific dimensions of cognition.

  3. Hydrological model uncertainty due to spatial evapotranspiration estimation methods

    Science.gov (United States)

    Yu, Xuan; Lamačová, Anna; Duffy, Christopher; Krám, Pavel; Hruška, Jakub

    2016-05-01

    Evapotranspiration (ET) continues to be a difficult process to estimate in seasonal and long-term water balances in catchment models. Approaches to estimate ET typically use vegetation parameters (e.g., leaf area index [LAI], interception capacity) obtained from field observation, remote sensing data, national or global land cover products, and/or simulated by ecosystem models. In this study we attempt to quantify the uncertainty that spatial evapotranspiration estimation introduces into hydrological simulations when the age of the forest is not precisely known. The Penn State Integrated Hydrologic Model (PIHM) was implemented for the Lysina headwater catchment, located 50°03‧N, 12°40‧E in the western part of the Czech Republic. The spatial forest patterns were digitized from forest age maps made available by the Czech Forest Administration. Two ET methods were implemented in the catchment model: the Biome-BGC forest growth sub-model (1-way coupled to PIHM) and with the fixed-seasonal LAI method. From these two approaches simulation scenarios were developed. We combined the estimated spatial forest age maps and two ET estimation methods to drive PIHM. A set of spatial hydrologic regime and streamflow regime indices were calculated from the modeling results for each method. Intercomparison of the hydrological responses to the spatial vegetation patterns suggested considerable variation in soil moisture and recharge and a small uncertainty in the groundwater table elevation and streamflow. The hydrologic modeling with ET estimated by Biome-BGC generated less uncertainty due to the plant physiology-based method. The implication of this research is that overall hydrologic variability induced by uncertain management practices was reduced by implementing vegetation models in the catchment models.

  4. Evaluating stream health based environmental justice model performance at different spatial scales

    Science.gov (United States)

    Daneshvar, Fariborz; Nejadhashemi, A. Pouyan; Zhang, Zhen; Herman, Matthew R.; Shortridge, Ashton; Marquart-Pyatt, Sandra

    2016-07-01

    This study evaluated the effects of spatial resolution on environmental justice analysis concerning stream health. The Saginaw River Basin in Michigan was selected since it is an area of concern in the Great Lakes basin. Three Bayesian Conditional Autoregressive (CAR) models (ordinary regression, weighted regression and spatial) were developed for each stream health measure based on 17 socioeconomic and physiographical variables at three census levels. For all stream health measures, spatial models had better performance compared to the two non-spatial ones at the census tract and block group levels. Meanwhile no spatial dependency was found at the county level. Multilevel Bayesian CAR models were also developed to understand the spatial dependency at the three levels. Results showed that considering level interactions improved models' prediction. Residual plots also showed that models developed at the block group and census tract (in contrary to county level models) are able to capture spatial variations.

  5. Spatial Models and Networks of Living Systems

    DEFF Research Database (Denmark)

    Juul, Jeppe Søgaard

    . Such systems are known to be stabilized by spatial structure. Finally, I analyse data from a large mobile phone network and show that people who are topologically close in the network have similar communication patterns. This main part of the thesis is based on six different articles, which I have co...... variables of the system. However, this approach disregards any spatial structure of the system, which may potentially change the behaviour drastically. An alternative approach is to construct a cellular automaton with nearest neighbour interactions, or even to model the system as a complex network...... with interactions defined by network topology. In this thesis I first describe three different biological models of ageing and cancer, in which spatial structure is important for the system dynamics. I then turn to describe characteristics of ecosystems consisting of three cyclically interacting species...

  6. Spatially explicit non-Mendelian diploid model

    CERN Document Server

    Lanchier, N; 10.1214/09-AAP598

    2009-01-01

    We introduce a spatially explicit model for the competition between type $a$ and type $b$ alleles. Each vertex of the $d$-dimensional integer lattice is occupied by a diploid individual, which is in one of three possible states or genotypes: $aa$, $ab$ or $bb$. We are interested in the long-term behavior of the gene frequencies when Mendel's law of segregation does not hold. This results in a voter type model depending on four parameters; each of these parameters measures the strength of competition between genes during meiosis. We prove that with or without a spatial structure, type $a$ and type $b$ alleles coexist at equilibrium when homozygotes are poor competitors. The inclusion of a spatial structure, however, reduces the parameter region where coexistence occurs.

  7. The 3-D global spatial data model foundation of the spatial data infrastructure

    CERN Document Server

    Burkholder, Earl F

    2008-01-01

    Traditional methods for handling spatial data are encumbered by the assumption of separate origins for horizontal and vertical measurements. Modern measurement systems operate in a 3-D spatial environment. The 3-D Global Spatial Data Model: Foundation of the Spatial Data Infrastructure offers a new model for handling digital spatial data, the global spatial data model or GSDM. The GSDM preserves the integrity of three-dimensional spatial data while also providing additional benefits such as simpler equations, worldwide standardization, and the ability to track spatial data accuracy with greater specificity and convenience. This groundbreaking spatial model incorporates both a functional model and a stochastic model to connect the physical world to the ECEF rectangular system. Combining horizontal and vertical data into a single, three-dimensional database, this authoritative monograph provides a logical development of theoretical concepts and practical tools that can be used to handle spatial data mo...

  8. Analysis of field-scale spatial correlations and variations of soil nutrients using geostatistics.

    Science.gov (United States)

    Liu, Ruimin; Xu, Fei; Yu, Wenwen; Shi, Jianhan; Zhang, Peipei; Shen, Zhenyao

    2016-02-01

    Spatial correlations and soil nutrient variations are important for soil nutrient management. They help to reduce the negative impacts of agricultural nonpoint source pollution. Based on the sampled available nitrogen (AN), available phosphorus (AP), and available potassium (AK), soil nutrient data from 2010, the spatial correlation, was analyzed, and the probabilities of the nutrient's abundance or deficiency were discussed. This paper presents a statistical approach to spatial analysis, the spatial correlation analysis (SCA), which was originally developed for describing heterogeneity in the presence of correlated variation and based on ordinary kriging (OK) results. Indicator kriging (IK) was used to assess the susceptibility of excess of soil nutrients based on crop needs. The kriged results showed there was a distinct spatial variability in the concentration of all three soil nutrients. High concentrations of these three soil nutrients were found near Anzhou. As the distance from the center of town increased, the concentration of the soil nutrients gradually decreased. Spatially, the relationship between AN and AP was negative, and the relationship between AP and AK was not clear. The IK results showed that there were few areas with a risk of AN and AP overabundance. However, almost the entire study region was at risk of AK overabundance. Based on the soil nutrient distribution results, it is clear that the spatial variability of the soil nutrients differed throughout the study region. This spatial soil nutrient variability might be caused by different fertilizer types and different fertilizing practices.

  9. Hierarchical spatial capture-recapture models: Modeling population density from stratified populations

    Science.gov (United States)

    Royle, J. Andrew; Converse, Sarah J.

    2014-01-01

    Capture–recapture studies are often conducted on populations that are stratified by space, time or other factors. In this paper, we develop a Bayesian spatial capture–recapture (SCR) modelling framework for stratified populations – when sampling occurs within multiple distinct spatial and temporal strata.We describe a hierarchical model that integrates distinct models for both the spatial encounter history data from capture–recapture sampling, and also for modelling variation in density among strata. We use an implementation of data augmentation to parameterize the model in terms of a latent categorical stratum or group membership variable, which provides a convenient implementation in popular BUGS software packages.We provide an example application to an experimental study involving small-mammal sampling on multiple trapping grids over multiple years, where the main interest is in modelling a treatment effect on population density among the trapping grids.Many capture–recapture studies involve some aspect of spatial or temporal replication that requires some attention to modelling variation among groups or strata. We propose a hierarchical model that allows explicit modelling of group or strata effects. Because the model is formulated for individual encounter histories and is easily implemented in the BUGS language and other free software, it also provides a general framework for modelling individual effects, such as are present in SCR models.

  10. Modeling Spatially Unrestricted Pedestrian Traffic on Footbridges

    DEFF Research Database (Denmark)

    Zivanovic, Stana; Pavic, Aleksandar; Ingólfsson, Einar Thór

    2010-01-01

    The research into modelling walking-induced dynamic loading and its effects on footbridge structures and people using them has been intensified in the last decade after some high profile vibration serviceability failures. In particular, the crowd induced loading, characterised by spatially...... restricted movement of pedestrians, has kept attracting attention of researchers. However, it is the normal spatially unrestricted pedestrian traffic, and its vertical dynamic loading component, that are most relevant for vibration serviceability checks for most footbridges. Despite the existence of numerous...... design procedures concerned with this loading, the current confidence in its modelling is low due to lack of verification of the models on as-built structures. This is the motivation behind reviewing the existing design procedures for modelling normal pedestrian traffic in this paper and evaluating...

  11. Modelling spatial density using continuous wavelet transforms

    Indian Academy of Sciences (India)

    D Sudheer Reddy; N Gopal Reddy; A K Anilkumar

    2013-02-01

    Due to increase in the satelite launch activities from many countries around the world the orbital debris issue has become a major concern for the space agencies to plan a collision-free orbit design. The risk of collisions is calculated using the in situ measurements and available models. Spatial density models are useful in understanding the long-term likelihood of a collision in a particular region of space and also helpful in pre-launch orbit planning. In this paper, we present a method of estimating model parameters such as number of peaks and peak locations of spatial density model using continuous wavelets. The proposed methodology was experimented with two line element data and the results are presented.

  12. Attribution of spatial and temporal variations in terrestrial methane flux over North America

    Directory of Open Access Journals (Sweden)

    X. F. Xu

    2010-11-01

    Full Text Available The attribution of spatial and temporal variations in terrestrial methane (CH4 flux is essential for assessing and mitigating CH4 emission from terrestrial ecosystems. In this study, we used a process-based model, the Dynamic Land Ecosystem Model (DLEM, in conjunction with spatial data of six major environmental factors to attribute the spatial and temporal variations in the terrestrial methane (CH4 flux over North America from 1979 to 2008 to six individual driving factors and their interaction. Over the past three decades, our simulations indicate that global change factors accumulatively contributed 23.51 ± 9.61 T g CH4-C (1 Tg = 1012 g emission over North America, among which ozone (O3 pollution led to a reduced CH4 emission by 2.30 ± 0.49 T g CH4-C. All other factors including climate variability, nitrogen (N deposition, elevated atmospheric carbon dioxide (CO2, N fertilizer application, and land conversion enhanced terrestrial CH4 emissions by 19.80 ± 12.42 T g CH4-C, 0.09 ± 0.02 T g CH4-C, 6.80 ± 0.86 T g CH4-C, 0.01 ± 0.001 T g CH4-C, and 3.95 ± 0.38 T g CH4-C, respectively, and interaction between/among these global change factors led to a decline of CH4 emission by 4.84 ± 7.74 T g CH4-C. Climate variability and O3 pollution suppressed, while other factors stimulated CH4 emission over the USA; climate variability significantly enhanced, while all the other factors exerted minor effects, positive or negative, on CH4 emission in Canada; Mexico functioned as a sink for atmospheric CH4 with a major contribution from climate change. Climatic variability dominated the inter-annual variations in terrestrial CH4 flux at both continental and country levels. Precipitation played an important role in

  13. Storm surge model based on variational data assimilation method

    Institute of Scientific and Technical Information of China (English)

    Shi-li HUANG; Jian XU; De-guan WANG; Dong-yan LU

    2010-01-01

    By combining computation and observation information,the variational data assimilation method has the ability to eliminate errors caused by the uncertainty of parameters in practical forecasting.It was applied to a storm surge model based on unstructured grids with high spatial resolution meant for improving the forecasting accuracy of the storm surge.By controlling the wind stress drag coefficient,the variation-based model was developed and validated through data assimilation tests in an actual storm surge induced by a typhoon.In the data assimilation tests,the model accurately identified the wind stress drag coefficient and obtained results close to the true state.Then,the actual storm surge induced by Typhoon 0515 was forecast by the developed model,and the results demonstrate its efficiency in practical application.

  14. Spatial Variations of Aftershock Parameters and their Relation to Geodetic Slip Models for the 2010 Mw8.8 Maule and the 2011 Mw9.0 Tohoku-oki Earthquakes

    Science.gov (United States)

    Zakharova, O.; Hainzl, S.; Lange, D.; Enescu, B.

    2017-01-01

    Recent development in analysis tools and deployments of the geodetic and seismic instruments give an opportunity to investigate aftershock sequences at local scales, which is important for the seismic hazard assessment. In particular, we study the dependencies between aftershock sequences properties and deformational/geological data on a scale of the rupture extension of megathrust earthquakes. For this goal we use, on one hand, published models of inter-, co- and postseismic slip and geological information and, on the other hand, aftershock parameters, obtained by fitting a modified Epidemic Type Aftershock Sequence (ETAS) model. The altered ETAS model takes into account the mainshock rupture extension and it distinguishes between primary and the secondary aftershock triggering involved in the total seismicity rate. We estimate the Spearman correlation coefficients between the spatially distributed aftershock parameters estimated by the modified ETAS model and crustal physical properties for the Maule 2010 Mw8.8 and the Tohoku-oki 2011 Mw9.0 aftershock sequences. We find that: (1) modified ETAS model outperforms the classical one, when the mainshock rupture extension cannot be neglected and represented as a point source; (2) anomalous aftershock parameters occur in the areas of the reactivated fault systems; (3) aftershocks, regardless of their generation, tend to occur in the areas of high coseismic slip gradient, afterslip and interseismic coupling; (4) aftershock seismic moment releases preferentially in regions of large coseismic slip, coseismic slip gradient and interseismically locked areas; (5) b value tends to be smaller in interseismically locked regions.

  15. Spatial Models and Networks of Living Systems

    DEFF Research Database (Denmark)

    Juul, Jeppe Søgaard

    variables of the system. However, this approach disregards any spatial structure of the system, which may potentially change the behaviour drastically. An alternative approach is to construct a cellular automaton with nearest neighbour interactions, or even to model the system as a complex network....... Such systems are known to be stabilized by spatial structure. Finally, I analyse data from a large mobile phone network and show that people who are topologically close in the network have similar communication patterns. This main part of the thesis is based on six different articles, which I have co...

  16. Modified Spatial Channel Model for MIMO Wireless Systems

    Directory of Open Access Journals (Sweden)

    Pekka Kyösti

    2007-12-01

    Full Text Available The third generation partnership Project's (3GPP spatial channel model (SCM is a stochastic channel model for MIMO systems. Due to fixed subpath power levels and angular directions, the SCM model does not show the degree of variation which is encountered in real channels. In this paper, we propose a modified SCM model which has random subpath powers and directions and still produces Laplace shape angular power spectrum. Simulation results on outage MIMO capacity with basic and modified SCM models show that the modified SCM model gives constantly smaller capacity values. Accordingly, it seems that the basic SCM gives too small correlation between MIMO antennas. Moreover, the variance in capacity values is larger using the proposed SCM model. Simulation results were supported by the outage capacity results from a measurement campaign conducted in the city centre of Oulu, Finland.

  17. Spatial Variation of the Relationship between PM2.5 Concentrations and Meteorological Parameters in China

    Directory of Open Access Journals (Sweden)

    Gang Lin

    2015-01-01

    Full Text Available Epidemiological studies around the world have reported that fine particulate matter (PM2.5 is closely associated with human health. The distribution of PM2.5 concentrations is influenced by multiple geographic and socioeconomic factors. Using a remote-sensing-derived PM2.5 dataset, this paper explores the relationship between PM2.5 concentrations and meteorological parameters and their spatial variance in China for the period 2001–2010. The spatial variations of the relationships between the annual average PM2.5, the annual average precipitation (AAP, and the annual average temperature (AAT were evaluated using the Geographically Weighted Regression (GWR model. The results indicated that PM2.5 had a strong and stable correlation with meteorological parameters. In particular, PM2.5 had a negative correlation with precipitation and a positive correlation with temperature. In addition, the relationship between the variables changed over space, and the strong negative correlation between PM2.5 and the AAP mainly appeared in the warm temperate semihumid region and northern subtropical humid region in 2001 and 2010, with some localized differences. The strong positive correlation between the PM2.5 and the AAT mainly occurred in the mid-temperate semiarid region, the humid, semihumid, and semiarid warm temperate regions, and the northern subtropical humid region in 2001 and 2010.

  18. Spatial and temporal variations of cortical growth during gyrogenesis in the developing ferret brain.

    Science.gov (United States)

    Knutsen, Andrew K; Kroenke, Christopher D; Chang, Yulin V; Taber, Larry A; Bayly, Philip V

    2013-02-01

    Spatial and temporal variations in cortical growth were studied in the neonatal ferret to illuminate the mechanisms of folding of the cerebral cortex. Cortical surface representations were created from magnetic resonance images acquired between postnatal day 4 and 35. Global measures of shape (e.g., surface area, normalized curvature, and sulcal depth) were calculated. In 2 ferrets, relative cortical growth was calculated between surfaces created from in vivo images acquired at P14, P21, and P28. The isocortical surface area transitions from a slower (12.7 mm(2)/day per hemisphere) to a higher rate of growth (36.7 mm(2)/day per hemisphere) approximately 13 days after birth, which coincides with the time of transition from neuronal proliferation to cellular morphological differentiation. Relative cortical growth increases as a function of relative geodesic distance from the origin of the transverse neurogenetic gradient and is related to the change in fractional diffusion anisotropy over the same time period. The methods presented here can be applied to study cortical growth during development in other animal models or human infants. Our results provide a quantitative spatial and temporal description of folding in cerebral cortex of the developing ferret brain, which will be important to understand the underlying mechanisms that drive folding.

  19. A variational formulation of electrostatics in a medium with spatially varying dielectric permittivity.

    Science.gov (United States)

    Jadhao, Vikram; Solis, Francisco J; Olvera de la Cruz, Monica

    2013-02-07

    In biological and synthetic materials, many important processes involve charges that are present in a medium with spatially varying dielectric permittivity. To accurately understand the role of electrostatic interactions in such systems, it is important to take into account the spatial dependence of the permittivity of the medium. However, due to the ensuing theoretical and computational challenges, this inhomogeneous dielectric response of the medium is often ignored or excessively simplified. We develop a variational formulation of electrostatics to accurately investigate systems that exhibit this inhomogeneous dielectric response. Our formulation is based on a true energy functional of the polarization charge density. The defining characteristic of a true energy functional is that at its minimum it evaluates to the actual value of the energy; this is a feature not found in many commonly used electrostatic functionals. We explore in detail the charged systems that exhibit sharp discontinuous change in dielectric permittivity, and we show that for this case our functional reduces to a functional of only the surface polarization charge density. We apply this reduced functional to study model problems for which analytical solutions are well known. We demonstrate, in addition, that the functional has many properties that make it ideal for use in molecular dynamics simulations.

  20. Spatial variation of dosimetric leaf gap and its impact on dose delivery

    Energy Technology Data Exchange (ETDEWEB)

    Kumaraswamy, Lalith K., E-mail: Lalith.Kumaraswamy@roswellpark.org [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 and Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Schmitt, Jonathan D. [Department of Radiation Medicine, RadAmerica, LLC-MedStar Health, Baltimore, Maryland 21237 (United States); Bailey, Daniel W. [Department of Radiation Oncology, Northside Hospital, Atlanta, Georgia 30342 (United States); Xu, Zheng Zheng [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 and Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14260 (United States); Podgorsak, Matthew B. [Department of Radiation Medicine, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263 (United States); Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14260 (United States)

    2014-11-01

    Purpose: During dose calculation, the Eclipse treatment planning system (TPS) retracts the multileaf collimator (MLC) leaf positions by half of the dosimetric leaf gap (DLG) value (measured at central axis) for all leaf positions in a dynamic MLC plan to accurately model the rounded leaf ends. The aim of this study is to map the variation of DLG along the travel path of each MLC leaf pair and quantify how this variation impacts delivered dose. Methods: 6 MV DLG values were measured for all MLC leaf pairs in increments of 1.0 cm (from the line intersecting the CAX and perpendicular to MLC motion) to 13.0 cm off axis distance at dmax. The measurements were performed on two Varian linear accelerators, both employing the Millennium 120-leaf MLCs. The measurements were performed at several locations in the beam with both a Sun Nuclear MapCHECK device and a PTW pinpoint ion chamber. Results: The measured DLGs for the middle 40 MLC leaf pairs (each 0.5 cm width) at positions along a line through the CAX and perpendicular to MLC leaf travel direction were very similar, varying maximally by only 0.2 mm. The outer 20 MLC leaf pairs (each 1.0 cm width) have much lower DLG values, about 0.3–0.5 mm lower than the central MLC leaf pair, at their respective central line position. Overall, the mean and the maximum variation between the 0.5 cm width leaves and the 1.0 cm width leaf pairs are 0.32 and 0.65 mm, respectively. Conclusions: The spatial variation in DLG is caused by the variation of intraleaf transmission through MLC leaves. Fluences centered on the CAX would not be affected since DLG does not vary; but any fluences residing significantly off axis with narrow sweeping leaves may exhibit significant dose differences. This is due to the fact that there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value utilized by the TPS for dose calculation. Since there are large differences in DLG between the 0.5 cm width

  1. Explaining growth variation over large spatial scales: Effects of temperature and food on walleye growth

    DEFF Research Database (Denmark)

    Mosgaard, Thomas; Venturelli, Paul; Lester, Nigel P.

    2012-01-01

    for among-lake variation in growth (e.g., food and temperature) has proved very difficult. Here, we use length at age and temperature data from hundreds of water bodies between 44⁰N to 53⁰N latitude to explain variation in immature growth of walleye (Sander vitreus), one of the most economically valuable...... the variation is productivity and a negative relationship indicates density-dependence. We found that variation in walleye growth among water bodies is largely explained by food productivity - not density-dependence. These results suggest that we can’t detect density-dependence among lakes when density......Most fishes exhibit strong spatial variation in growth. Because fish growth and production are tightly linked, quantifying and explaining variation in growth can mean the difference between successful management and unforeseen collapse. However, disentangling the factors that are responsible...

  2. Community functional responses to soil and climate at multiple spatial scales: when does intraspecific variation matter?

    Directory of Open Access Journals (Sweden)

    Andrew Siefert

    Full Text Available Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA, and leaf dry matter content (LDMC. We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.

  3. Community functional responses to soil and climate at multiple spatial scales: when does intraspecific variation matter?

    Science.gov (United States)

    Siefert, Andrew; Fridley, Jason D; Ritchie, Mark E

    2014-01-01

    Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.

  4. On the total variation dictionary model.

    Science.gov (United States)

    Zeng, Tieyong; Ng, Michael K

    2010-03-01

    The goal of this paper is to provide a theoretical study of a total variation (TV) dictionary model. Based on the properties of convex analysis and bounded variation functions, the existence of solutions of the TV dictionary model is proved. We then show that the dual form of the model can be given by the minimization of the sum of the l(1) -norm of the dual solution and the Bregman distance between the curvature of the primal solution and the subdifferential of TV norm of the dual solution. This theoretical result suggests that the dictionary must represent sparsely the curvatures of solution image in order to obtain a better denoising performance.

  5. Explaining spatial heterogeneity in population dynamics and genetics from spatial variation in resources for a large herbivore.

    Science.gov (United States)

    Contasti, Adrienne L; Tissier, Emily J; Johnstone, Jill F; McLoughlin, Philip D

    2012-01-01

    Fine-scale spatial variation in genetic relatedness and inbreeding occur across continuous distributions of several populations of vertebrates; however, the basis of observed variation is often left untested. Here we test the hypothesis that prior observations of spatial patterns in genetics for an island population of feral horses (Sable Island, Canada) were the result of spatial variation in population dynamics, itself based in spatial heterogeneity in underlying habitat quality. In order to assess how genetic and population structuring related to habitat, we used hierarchical cluster analysis of water sources and an indicator analysis of the availability of important forage species to identify a longitudinal gradient in habitat quality along the length of Sable Island. We quantify a west-east gradient in access to fresh water and availability of two important food species to horses: sandwort, Honckenya peploides, and beach pea, Lathyrus japonicas. Accordingly, the population clusters into three groups that occupy different island segments (west, central, and east) that vary markedly in their local dynamics. Density, body condition, and survival and reproduction of adult females were highest in the west, followed by central and east areas. These results mirror a previous analysis of genetics, which showed that inbreeding levels are highest in the west (with outbreeding in the east), and that there are significant differences in fixation indices among groups of horses along the length of Sable Island. Our results suggest that inbreeding depression is not an important limiting factor to the horse population. We conclude that where habitat gradients exist, we can anticipate fine-scale heterogeneity in population dynamics and hence genetics.

  6. Spatial Modeling of Iron Transformations Within Artificial Soil Aggregates

    Science.gov (United States)

    Kausch, M.; Meile, C.; Pallud, C.

    2008-12-01

    Structured soils exhibit significant variations in transport characteristics at the aggregate scale. Preferential flow occurs through macropores while predominantly diffusive exchange takes place in intra-aggregate micropores. Such environments characterized by mass transfer limitations are conducive to the formation of small-scale chemical gradients and promote strong spatial variation in processes controlling the fate of redox-sensitive elements such as Fe. In this study, we present a reactive transport model used to spatially resolve iron bioreductive processes occurring within a spherical aggregate at the interface between advective and diffusive domains. The model is derived from current conceptual models of iron(hydr)oxide (HFO) transformations and constrained by literature and experimental data. Data were obtained from flow-through experiments on artificial soil aggregates inoculated with Shewanella putrefaciens strain CN32, and include the temporal evolution of the bulk solution composition, as well as spatial information on the final solid phase distribution within aggregates. With all iron initially in the form of ferrihydrite, spatially heterogeneous formation of goethite/lepidocrocite, magnetite and siderite was observed during the course of the experiments. These transformations were reproduced by the model, which ascribes a central role to divalent iron as a driver of HFO transformations and master variable in the rate laws of the considered reaction network. The predicted dissolved iron breakthrough curves also match the experimental ones closely. Thus, the computed chemical concentration fields help identify factors governing the observed trends in the solid phase distribution patterns inside the aggregate. Building on a mechanistic description of transformation reactions, fluid flow and solute transport, the model was able to describe the observations and hence illustrates the importance of small-scale gradients and dynamics of bioreductive

  7. Sparse modeling of spatial environmental variables associated with asthma.

    Science.gov (United States)

    Chang, Timothy S; Gangnon, Ronald E; David Page, C; Buckingham, William R; Tandias, Aman; Cowan, Kelly J; Tomasallo, Carrie D; Arndt, Brian G; Hanrahan, Lawrence P; Guilbert, Theresa W

    2015-02-01

    Geographically distributed environmental factors influence the burden of diseases such as asthma. Our objective was to identify sparse environmental variables associated with asthma diagnosis gathered from a large electronic health record (EHR) dataset while controlling for spatial variation. An EHR dataset from the University of Wisconsin's Family Medicine, Internal Medicine and Pediatrics Departments was obtained for 199,220 patients aged 5-50years over a three-year period. Each patient's home address was geocoded to one of 3456 geographic census block groups. Over one thousand block group variables were obtained from a commercial database. We developed a Sparse Spatial Environmental Analysis (SASEA). Using this method, the environmental variables were first dimensionally reduced with sparse principal component analysis. Logistic thin plate regression spline modeling was then used to identify block group variables associated with asthma from sparse principal components. The addresses of patients from the EHR dataset were distributed throughout the majority of Wisconsin's geography. Logistic thin plate regression spline modeling captured spatial variation of asthma. Four sparse principal components identified via model selection consisted of food at home, dog ownership, household size, and disposable income variables. In rural areas, dog ownership and renter occupied housing units from significant sparse principal components were associated with asthma. Our main contribution is the incorporation of sparsity in spatial modeling. SASEA sequentially added sparse principal components to Logistic thin plate regression spline modeling. This method allowed association of geographically distributed environmental factors with asthma using EHR and environmental datasets. SASEA can be applied to other diseases with environmental risk factors.

  8. Fate modeling of phenanthrene with regional variation in Tianjin, China

    Energy Technology Data Exchange (ETDEWEB)

    Tao, S.; Cao, H.; Liu, W.; [and others] [Peking University, Beijing (China). Dept. of Urban and Environmental Sciences

    2003-06-01

    A multimedia fate model with spatially resolved air and soil phases was developed and evaluated. The model was used for calculation of phenanthrene concentrations in air, water, soil and sediment in Tianjin area and transport flxues between the adjacent bulk phases under steady-state assumption. Both air and soil phases were divided into 3113 individual compartments of 4 km{sup 2} each to assess the spatial variation of phenanthrene concentrations and fluxes. Independently measured phenanthrene concentrations in air, water and soil were used for model validation. The large amount of coal used seems to be the major source of phenanthrene in the Tainjin area. The spatial distribution patterns of phenanthrene in both air and soil were well modeled. Spatially, however, the model overestimated the soil phenanthrene level at low concentration range and underestimated it at high concentration range. The calculated distribution of phenanthrene in the air matches well with the emission from fossil fuel combustion, while the calculated distribution pattern in the soil is similar to that observed. 36 refs., 10 figs.

  9. The Massive Star Population in M101. II. Spatial Variations in the Recent Star Formation History

    Science.gov (United States)

    Grammer, Skyler; Humphreys, Roberta M.

    2014-09-01

    We investigate star formation history (SFH) as a function of radius in M101 using archival Hubble Space Telescope Advanced Camera for Surveys photometry. We derive the SFH from the resolved stellar populations in five 2' wide annuli. Binning the SFH into time frames corresponding to stellar populations traced by Hα, far-ultraviolet, and near-ultraviolet emission, we find that the fraction of stellar populations young enough to contribute in Hα is 15%-35% in the inner regions, compared to less than 5% in the outer regions. This provides a sufficient explanation for the lack of Hα emission at large radii. We also model the blue to red supergiant ratio in our five annuli, examine the effects that a metallicity gradient and variable SFH have on the predicted ratios, and compare to the observed values. We find that the radial behavior of our modeled blue to red supergiant ratios is highly sensitive to both spatial variations in the SFH and metallicity. Incorporating the derived SFH into modeled ratios, we find that we are able to reproduce the observed values at large radii (low metallicity), but at small radii (high metallicity) the modeled and observed ratios are discrepant.

  10. Spatially explicit modeling in ecology: A review

    Science.gov (United States)

    DeAngelis, Donald L.; Yurek, Simeon

    2017-01-01

    The use of spatially explicit models (SEMs) in ecology has grown enormously in the past two decades. One major advancement has been that fine-scale details of landscapes, and of spatially dependent biological processes, such as dispersal and invasion, can now be simulated with great precision, due to improvements in computer technology. Many areas of modeling have shifted toward a focus on capturing these fine-scale details, to improve mechanistic understanding of ecosystems. However, spatially implicit models (SIMs) have played a dominant role in ecology, and arguments have been made that SIMs, which account for the effects of space without specifying spatial positions, have an advantage of being simpler and more broadly applicable, perhaps contributing more to understanding. We address this debate by comparing SEMs and SIMs in examples from the past few decades of modeling research. We argue that, although SIMs have been the dominant approach in the incorporation of space in theoretical ecology, SEMs have unique advantages for addressing pragmatic questions concerning species populations or communities in specific places, because local conditions, such as spatial heterogeneities, organism behaviors, and other contingencies, produce dynamics and patterns that usually cannot be incorporated into simpler SIMs. SEMs are also able to describe mechanisms at the local scale that can create amplifying positive feedbacks at that scale, creating emergent patterns at larger scales, and therefore are important to basic ecological theory. We review the use of SEMs at the level of populations, interacting populations, food webs, and ecosystems and argue that SEMs are not only essential in pragmatic issues, but must play a role in the understanding of causal relationships on landscapes.

  11. Capturing Appearance Variation in Active Appearance Models

    NARCIS (Netherlands)

    Van der Maaten, L.J.P.; Hendriks, E.A.

    2010-01-01

    The paper presents an extension of active appearance models (AAMs) that is better capable of dealing with the large variation in face appearance that is encountered in large multi-person face data sets. Instead of the traditional PCA-based texture model, our extended AAM employs a mixture of probabi

  12. Variation in soil carbon dioxide efflux at two spatial scales in a topographically complex boreal forest

    Science.gov (United States)

    Kelsey, Katharine C.; Wickland, Kimberly P.; Striegl, Rob; Neff, Jason C.

    2012-01-01

    Carbon dynamics of high-latitude regions are an important and highly uncertain component of global carbon budgets, and efforts to constrain estimates of soil-atmosphere carbon exchange in these regions are contingent on accurate representations of spatial and temporal variability in carbon fluxes. This study explores spatial and temporal variability in soilatmosphere carbon dynamics at both fine and coarse spatial scales in a high-elevation, permafrost-dominated boreal black spruce forest. We evaluate the importance of landscape-level investigations of soil-atmosphere carbon dynamics by characterizing seasonal trends in soil-atmosphere carbon exchange, describing soil temperature-moisture-respiration relations, and quantifying temporal and spatial variability at two spatial scales: the plot scale (0–5 m) and the landscape scale (500–1000 m). Plot-scale spatial variability (average variation on a given measurement day) in soil CO2 efflux ranged from a coefficient of variation (CV) of 0.25 to 0.69, and plot-scale temporal variability (average variation of plots across measurement days) in efflux ranged from a CV of 0.19 to 0.36. Landscape-scale spatial and temporal variability in efflux was represented by a CV of 0.40 and 0.31, respectively, indicating that plot-scale spatial variability in soil respiration is as great as landscape-scale spatial variability at this site. While soil respiration was related to soil temperature at both the plot- and landscape scale, landscape-level descriptions of soil moisture were necessary to define soil respiration-moisture relations. Soil moisture variability was also integral to explaining temporal variability in soil respiration. Our results have important implications for research efforts in high-latitude regions where remote study sites make landscape-scale field campaigns challenging.

  13. Spatial-Temporal Variation and Prediction of Rainfall in Northeastern Nigeria

    Directory of Open Access Journals (Sweden)

    Umar M. Bibi

    2014-09-01

    Full Text Available In Northeastern Nigeria seasonal rainfall is critical for the availability of water for domestic use through surface and sub-surface recharge and agricultural production, which is mostly rain fed. Variability in rainfall over the last 60 years is the main cause for crop failure and water scarcity in the region, particularly, due to late onset of rainfall, short dry spells and multi-annual droughts. In this study, we analyze 27 years (1980–2006 of gridded daily rainfall data obtained from a merged dataset by the National Centre for Environmental Prediction and Climate Research Unit reanalysis data (NCEP-CRU for spatial-temporal variability of monthly amounts and frequency in rainfall and rainfall trends. Temporal variability was assessed using the percentage coefficient of variation and temporal trends in rainfall were assessed using maps of linear regression slopes for the months of May through October. These six months cover the period of the onset and cessation of the wet season throughout the region. Monthly rainfall amount and frequency were then predicted over a 24-month period using the Auto Regressive Integrated Moving Average (ARIMA Model. The predictions were evaluated using NCEP-CRU data for the same period. Kolmogorov Smirnov test results suggest that despite there are some months during the wet season (May–October when there is no significant agreement (p < 0.05 between the monthly distribution of the values of the model and the corresponding 24-month NCEP-CRU data, the model did better than simply replicating the long term mean of the data used for the prediction. Overall, the model does well in areas and months with lower temporal rainfall variability. Maps of the coefficient of variation and regression slopes are presented to indicate areas of high rainfall variability and water deficit over the period under study. The implications of these results for future policies on Agriculture and Water Management in the region are

  14. Global budget of atmospheric carbonyl sulfide: Temporal and spatial variations of the dominant sources and sinks

    Science.gov (United States)

    Kettle, A. J.; Kuhn, U.; von Hobe, M.; Kesselmeier, J.; Andreae, M. O.

    2002-11-01

    The spatial and temporal variability of the global fluxes of carbonyl sulfide (COS) is discussed together with possible implications for total column atmospheric COS loading. The input of COS into the atmosphere is calculated as the sum of all known direct sources of COS plus the conversion of carbon disulfide (CS2) and dimethyl sulfide (DMS) to COS by atmospheric oxidation processes. Recent models are used to predict COS, CS2, and DMS release from the oceans and COS uptake by soils, plants, and oceans. This forward approach to constructing global integrated COS fluxes has a large associated range of uncertainty. The best guess global annual-integrated COS net flux estimate does not differ from zero within the range of estimated uncertainty, consistent with the observed absence of long-term trends in atmospheric COS loading. Interestingly, the hemispheric time-dependent monthly fluxes are very close in phase for the Northern and Southern Hemispheres. The monthly variation of the Northern Hemisphere flux seems to be driven primarily by high COS vegetation uptake in summer, while the monthly variation of the Southern Hemisphere flux appears to be driven mostly by high oceanic fluxes of COS, CS2, and DMS in summer.

  15. [Analysis of vegetation spatial and temporal variations in Qinghai Province based on remote sensing].

    Science.gov (United States)

    Wang, Li-wen; Wei, Ya-xing; Niu, Zheng

    2008-06-01

    1 km MODIS NDVI time series data combining with decision tree classification, supervised classification and unsupervised classification was used to classify land cover type of Qinghai Province into 14 classes. In our classification system, sparse grassland and sparse shrub were emphasized, and their spatial distribution locations were labeled. From digital elevation model (DEM) of Qinghai Province, five elevation belts were achieved, and we utilized geographic information system (GIS) software to analyze vegetation cover variation on different elevation belts. Our research result shows that vegetation cover in Qinghai Province has been improved in recent five years. Vegetation cover area increases from 370047 km2 in 2001 to 374576 km2 in 2006, and vegetation cover rate increases by 0.63%. Among five grade elevation belts, vegetation cover ratio of high mountain belt is the highest (67.92%). The area of middle density grassland in high mountain belt is the largest, of which area is 94 003 km2. Increased area of dense grassland in high mountain belt is the greatest (1280 km2). During five years, the biggest variation is the conversion from sparse grassland to middle density grassland in high mountain belt, of which area is 15931 km2.

  16. A nonlocal spatial model for Lyme disease

    Science.gov (United States)

    Yu, Xiao; Zhao, Xiao-Qiang

    2016-07-01

    This paper is devoted to the study of a nonlocal and time-delayed reaction-diffusion model for Lyme disease with a spatially heterogeneous structure. In the case of a bounded domain, we first prove the existence of the positive steady state and a threshold type result for the disease-free system, and then establish the global dynamics for the model system in terms of the basic reproduction number. In the case of an unbound domain, we obtain the existence of the disease spreading speed and its coincidence with the minimal wave speed. At last, we use numerical simulations to verify our analytic results and investigate the influence of model parameters and spatial heterogeneity on the disease infection risk.

  17. Quantitative Monitoring for Enhanced Geothermal Systems Using Double-Difference Waveform Inversion with Spatially-Variant Total-Variation Regularization

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Youzuo [Los Alamos National Laboratory; Huang, Lianjie [Los Alamos National Laboratory; Zhang, Zhigang [Los Alamos National Laboratory

    2011-01-01

    Double-difference waveform inversion is a promising tool for quantitative monitoring for enhanced geothermal systems (EGS). The method uses time-lapse seismic data to jointly inverts for reservoir changes. Due to the ill-posedness of waveform inversion, it is a great challenge to obtain reservoir changes accurately and efficiently, particularly when using timelapse seismic reflection data. To improve reconstruction, we develop a spatially-variant total-variation regularization scheme into double-difference waveform inversion to improve the inversion accuracy and robustness. The new regularization scheme employs different regularization parameters in different regions of the model to obtain an optimal regularization in each area. We compare the results obtained using a spatially-variant parameter with those obtained using a constant regularization parameter. Utilizing a spatially-variant regularization scheme, the target monitoring regions are well reconstructed and the image noise is significantly reduced outside the monitoring regions. Our numerical examples demonstrate that the spatially-variant total-variation regularization scheme provides the flexibility to regularize local regions based on the a priori spatial information without increasing computational costs and the computer memory requirement.

  18. Linking spatial and dynamic models for traffic maneuvers

    DEFF Research Database (Denmark)

    Olderog, Ernst-Rüdiger; Ravn, Anders Peter; Wisniewski, Rafal

    2015-01-01

    For traffic maneuvers of multiple vehicles on highways we build an abstract spatial and a concrete dynamic model. In the spatial model we show the safety (collision freedom) of lane-change maneuvers. By linking the spatial and dynamic model via suitable refinements of the spatial atoms to distance...

  19. Spatial and temporal variation of fish assemblages in a subtropical small stream of the Huangshan Mountain

    Directory of Open Access Journals (Sweden)

    Yunzhi YAN,Shan HE, Ling CHU, Xiuying XIANG, Yanju JIA, Juan TAO, Yifeng CHEN

    2010-12-01

    Full Text Available Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities (ANOSIM, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis (NMS, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%: the upper, middle and lower groups. Following analysis of similarity percentages of species contributions (SIMPER, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst the three groups. Standard Deviation Redundancy Analysis (RDA suggested that habitat structure (such as elevation, substrate, and flow velocity contributed to the spatial and temporal pattern of fish assemblages in the Puxi Stream. In conclusion, the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 (6

  20. Predicting spatial variations of tree species richness in tropical forests from high-resolution remote sensing.

    Science.gov (United States)

    Fricker, Geoffrey A; Wolf, Jeffrey A; Saatchi, Sassan S; Gillespie, Thomas W

    2015-10-01

    There is an increasing interest in identifying theories, empirical data sets, and remote-sensing metrics that can quantify tropical forest alpha diversity at a landscape scale. Quantifying patterns of tree species richness in the field is time consuming, especially in regions with over 100 tree species/ha. We examine species richness in a 50-ha plot in Barro Colorado Island in Panama and test if biophysical measurements of canopy reflectance from high-resolution satellite imagery and detailed vertical forest structure and topography from light detection and ranging (lidar) are associated with species richness across four tree size classes (>1, 1-10, >10, and >20 cm dbh) and three spatial scales (1, 0.25, and 0.04 ha). We use the 2010 tree inventory, including 204,757 individuals belonging to 301 species of freestanding woody plants or 166 ± 1.5 species/ha (mean ± SE), to compare with remote-sensing data. All remote-sensing metrics became less correlated with species richness as spatial resolution decreased from 1.0 ha to 0.04 ha and tree size increased from 1 cm to 20 cm dbh. When all stems with dbh > 1 cm in 1-ha plots were compared to remote-sensing metrics, standard deviation in canopy reflectance explained 13% of the variance in species richness. The standard deviations of canopy height and the topographic wetness index (TWI) derived from lidar were the best metrics to explain the spatial variance in species richness (15% and 24%, respectively). Using multiple regression models, we made predictions of species richness across Barro Colorado Island (BCI) at the 1-ha spatial scale for different tree size classes. We predicted variation in tree species richness among all plants (adjusted r² = 0.35) and trees with dbh > 10 cm (adjusted r² = 0.25). However, the best model results were for understory trees and shrubs (dbh 1-10 cm) (adjusted r² = 0.52) that comprise the majority of species richness in tropical forests. Our results indicate that high

  1. Developing a modelling for the spatial data infrastructure

    CSIR Research Space (South Africa)

    Hjelmager, J

    2005-07-01

    Full Text Available The Commission on Spatial Data Standards of the International Cartographic Association (ICA) is working on defining spatial models and technical characteristics of a Spatial Data Infrastructure (SDI). To date, this work has been restricted...

  2. Factor Copula Models for Replicated Spatial Data

    KAUST Repository

    Krupskii, Pavel

    2016-12-19

    We propose a new copula model that can be used with replicated spatial data. Unlike the multivariate normal copula, the proposed copula is based on the assumption that a common factor exists and affects the joint dependence of all measurements of the process. Moreover, the proposed copula can model tail dependence and tail asymmetry. The model is parameterized in terms of a covariance function that may be chosen from the many models proposed in the literature, such as the Matérn model. For some choice of common factors, the joint copula density is given in closed form and therefore likelihood estimation is very fast. In the general case, one-dimensional numerical integration is needed to calculate the likelihood, but estimation is still reasonably fast even with large data sets. We use simulation studies to show the wide range of dependence structures that can be generated by the proposed model with different choices of common factors. We apply the proposed model to spatial temperature data and compare its performance with some popular geostatistics models.

  3. GWR-PM - Spatial variation relationship analysis with Geographically Weighted Regression (GWR) - An application at Peninsular Malaysia

    Science.gov (United States)

    Jamhuri, J.; Azhar, B. M. S.; Puan, C. L.; Norizah, K.

    2016-06-01

    GWR-PM has been developed exclusively for decision makers in Peninsular Malaysia and the purpose is to provide them with additional flexibility in analysing spatial variation. While GWR extension analysis in ArcMap application has a universal coordinate system, GWR-PM is specifically designed with Peninsular Malaysia's coordinate system of Kertau RSO Malaya Meter. This paper presents the development of GWR-PM model by using a model builder, the application of which is to examine the forest fire risk at North Selangor Peat Swamp Forest. This model can be extended and improved by using ArcGIS language of phyton.

  4. Modeling the variation trends of glacier systems

    Directory of Open Access Journals (Sweden)

    Z. Xie

    2013-01-01

    Full Text Available The basic principles and methods for a functional glacier systems model are introduced and applied for glaciers of Northwest China. When running the model we assume that a glacier system is under steady state conditions in the initial year. The median size of a glacier system is used as representative for the system. The curve of glacier area distribution against elevation is used to compute the increase in equilibrium line altitude (ELA, and the annual glacier ablation is calculated using a global formula a = 1.33(9.66 + ts².⁸⁵ [4, p. 96]. The net mass balance near the ELA under steady state conditions represents the net mass balance of the whole glacier system, and the time required for glacier runoff to return to the initial year level is calculated according to the law of glacier runoff variation, and used to calculate the variation of glacier area. The variation of glacier runoff is modeled according to ablation at the ELA, and the variation of glacier volume is modeled according to the absolute value of the mass balance. The observed changes in surveyed glaciers in China over recent decades were broadly consistent with predictions of the glacier system model. The model therefore offers a reliable method for the prediction of changes in glacier systems in response to changing climate.

  5. The Massive Star Population in M101. II. Spatial Variations in the Recent Star Formation History

    CERN Document Server

    Grammer, Skyler

    2014-01-01

    We investigate the star formation history (SFH) as a function of radius in M101 using archival HST/ACS photometry. We derive the SFH from the resolved stellar populations in five 2' wide annuli. Binning the SFH into time frames corresponding to stellar populations traced by H$\\alpha$, far ultraviolet (FUV), and near ultraviolet (NUV) emission, we find that the fraction of stellar populations young enough to contribute in H$\\alpha$ is 15%-35% in the inner regions, compared to less than 5% in the outer regions. This provides a sufficient explanation for the lack of H$\\alpha$ emission at large radii. We also model the blue to red supergiant ratio in our five annuli, examine the effects that a metallicity gradient and variable SFH have on the predicted ratios, and compare to the observed values. We find that the radial behavior of our modeled blue to red supergiant ratios is highly sensitive to both spatial variations in the SFH and metallicity. Incorporating the derived SFH into modeled ratios, we find that we a...

  6. Delay Variation Model with Two Service Queues

    Directory of Open Access Journals (Sweden)

    Filip Rezac

    2010-01-01

    Full Text Available Delay in VoIP technology is very unpleasant issue and therefore a voice packets prioritization must be ensured. To maintain the high call quality a maximum information delivery time from the sender to the recipient is set to 150 ms. This paper focuses on the design of a mathematical model of end-to-end delay of a VoIP connection, in particular on a delay variation. It describes all partial delay components and mechanisms, their generation, facilities and mathematical formulations. A new approach to the delay variation model is presented and its validation has been done by experimention.

  7. Single Plant Root System Modeling under Soil Moisture Variation

    Science.gov (United States)

    Yabusaki, S.; Fang, Y.; Chen, X.; Scheibe, T. D.

    2016-12-01

    A prognostic Virtual Plant-Atmosphere-Soil System (vPASS) model is being developed that integrates comprehensively detailed mechanistic single plant modeling with microbial, atmospheric, and soil system processes in its immediate environment. Three broad areas of process module development are targeted: Incorporating models for root growth and function, rhizosphere interactions with bacteria and other organisms, litter decomposition and soil respiration into established porous media flow and reactive transport models Incorporating root/shoot transport, growth, photosynthesis and carbon allocation process models into an integrated plant physiology model Incorporating transpiration, Volatile Organic Compounds (VOC) emission, particulate deposition and local atmospheric processes into a coupled plant/atmosphere model. The integrated plant ecosystem simulation capability is being developed as open source process modules and associated interfaces under a modeling framework. The initial focus addresses the coupling of root growth, vascular transport system, and soil under drought scenarios. Two types of root water uptake modeling approaches are tested: continuous root distribution and constitutive root system architecture. The continuous root distribution models are based on spatially averaged root development process parameters, which are relatively straightforward to accommodate in the continuum soil flow and reactive transport module. Conversely, the constitutive root system architecture models use root growth rates, root growth direction, and root branching to evolve explicit root geometries. The branching topologies require more complex data structures and additional input parameters. Preliminary results are presented for root model development and the vascular response to temporal and spatial variations in soil conditions.

  8. Research of ERP model system of spatial data warehouse

    Institute of Scientific and Technical Information of China (English)

    CHEN Xue-long; WANG Yan-zhang

    2004-01-01

    The broad sharing of spatial information is demanded in the infrastructure construction of spatial data in our country. And the spatial data warehouse realizes the effective management and sharing of spatial information serving as an efficient tool. This article proposes ERP model system that of general-decision-oriented for constructing spatial data warehouse from the aspect of decision application. In the end of article, the construction process of spatial data warehouse based on ERP model system is discussed.

  9. Spatial Aggregation: Data Model and Implementation

    CERN Document Server

    Gomez, Leticia; Kuijpers, Bart; Vaisman, Alejandro

    2007-01-01

    Data aggregation in Geographic Information Systems (GIS) is only marginally present in commercial systems nowadays, mostly through ad-hoc solutions. In this paper, we first present a formal model for representing spatial data. This model integrates geographic data and information contained in data warehouses external to the GIS. We define the notion of geometric aggregation, a general framework for aggregate queries in a GIS setting. We also identify the class of summable queries, which can be efficiently evaluated by precomputing the overlay of two or more of the thematic layers involved in the query. We also sketch a language, denoted GISOLAP-QL, for expressing queries that involve GIS and OLAP features. In addition, we introduce Piet, an implementation of our proposal, that makes use of overlay precomputation for answering spatial queries (aggregate or not). Our experimental evaluation showed that for a certain class of geometric queries with or without aggregation, overlay precomputation outperforms R-tre...

  10. Variation in coastal Antarctic microbial community composition at sub-mesoscale: spatial distance or environmental filtering?

    Science.gov (United States)

    Moreno-Pino, Mario; De la Iglesia, Rodrigo; Valdivia, Nelson; Henríquez-Castilo, Carlos; Galán, Alexander; Díez, Beatriz; Trefault, Nicole

    2016-07-01

    Spatial environmental heterogeneity influences diversity of organisms at different scales. Environmental filtering suggests that local environmental conditions provide habitat-specific scenarios for niche requirements, ultimately determining the composition of local communities. In this work, we analyze the spatial variation of microbial communities across environmental gradients of sea surface temperature, salinity and photosynthetically active radiation and spatial distance in Fildes Bay, King George Island, Antarctica. We hypothesize that environmental filters are the main control of the spatial variation of these communities. Thus, strong relationships between community composition and environmental variation and weak relationships between community composition and spatial distance are expected. Combining physical characterization of the water column, cell counts by flow cytometry, small ribosomal subunit genes fingerprinting and next generation sequencing, we contrast the abundance and composition of photosynthetic eukaryotes and heterotrophic bacterial local communities at a submesoscale. Our results indicate that the strength of the environmental controls differed markedly between eukaryotes and bacterial communities. Whereas eukaryotic photosynthetic assemblages responded weakly to environmental variability, bacteria respond promptly to fine-scale environmental changes in this polar marine system.

  11. [Characteristics of spatial variation of soil nutrients in sloping field in a gorge karst region, southwest China].

    Science.gov (United States)

    Fan, Fu-Jing; Song, Tong-Qing; Huang, Guo-Qin; Zeng, Fu-Ping; Peng, Wan-Xia; Du, Hu; Lu, Shi-Yang; Shi, Wei-Wei; Tan, Qiu-Jin

    2014-01-01

    Based on a grid (20 m x 20 m) sampling, spatial heterogeneity and pattern of soil nutrients in sloping field in the gorge karst region, southwestern China, were explored by using classical statistics and geostatistics methods. The results showed that soil nutrient contents in slope field in the canyon karst region were more abundant, where pH value had a weak variation and the soil organic matter (SOM) had a moderate degree of variation. All the soil nutrients had moderate or strong variation with an order of available phosphorus (AP) > total potassium (TK) > SOM > alkaline nitrogen (AN) > total nitrogen (TN) > total phosphorus (TP) > available potassium (AK). All of the soil nutrients had a good spatial autocorrelation and the autocorrelation function performed in the same law of developing from positive to negative direction with the inflection point ranged from 80 to 100 m. In addition, the Moran's I was small for TK and AP while large for other nutrients. Characteristics of spatial variation differed among soil nutrients. Exponential model fitted best for TK and AP, in which the ratio of nugget to sill (C0/(C0 + C)) and the range (A) were small and the fractal dimension (D) was high, showed a strong spatial correlation. Spherical model fitted best for other soil nutrients, with C0/(C0 + C) , the range (A) and D showing a moderate autocorrelation. Kriging analysis clearly indicated that pH, SOM, TN, TP and AN were distributed in a concave pattern, while AP and AK had fragmented patch distribution. Therefore, vegetation, topography, human disturbance and strong heterogeneity of microhabitats are main factors leading to the differences in patterns of soil nutrients on the sloping land in the gorge karst region.

  12. Human Plague Risk: Spatial-Temporal Models

    Science.gov (United States)

    Pinzon, Jorge E.

    2010-01-01

    This chpater reviews the use of spatial-temporal models in identifying potential risks of plague outbreaks into the human population. Using earth observations by satellites remote sensing there has been a systematic analysis and mapping of the close coupling between the vectors of the disease and climate variability. The overall result is that incidence of plague is correlated to positive El Nino/Southem Oscillation (ENSO).

  13. Spatial and temporal variations of ponded infiltration in a grid of permanent infiltration rings

    Science.gov (United States)

    Votrubová, Jana; Dohnal, Michal; Dušek, Jaromír; Vogel, Tomáš; Tesař, Miroslav; Císlerová, Milena

    2016-04-01

    The soil at Liz experimental site (Volynka headwater catchment, Sumava Mountains, southern Bohemia) has been subject to a long term research on the soil infiltration properties since 2003. For this purpose, 18 permanent infiltration rings were installed at a gently sloped grass-covered experimental plot (300 sq.m). Using this set-up, the single-ring ponded infiltration experiments have been conducted annually. Since 2005, a procedure of repeating the same ponded infiltration experiments in two successive days has been implemented. For the soil type of the study area (sandy loam developed upon gneiss bedrock), a large spatial variability of soil hydraulic properties had been reported before. The focus of the present study has been primarily the temporal variability of the soil infiltration properties. Results of a supplementary dye-tracer experiment conducted in 2005 demonstrate that in the soil studied the infiltration process is strongly dominated by preferential flow. As expected, infiltration rates varied considerably among the infiltration ring. With regard to the impact of the initial soil moisture conditions, general decrease of the infiltration rates observed on two subsequent days was detected. Surprisingly, the spatial variations between separate measuring points were vastly overridden by a huge overall increase of the infiltration rates observed throughout the years. The observed variability of the experimental data was further examined in numerical simulations of hypothetical scenarios reflecting possible variations of soil profile and experimental set-up. Axisymmetric 3D simulations were performed using S2D code. The dual-continuum model was able to describe part of the variability of infiltration curves associated with soil structure heterogeneity. None of the tested factors could explain the wide range of infiltration rate variations observed. Nevertheless, better agreement between simulated and observed infiltration characteristics could be achieved

  14. Strontium isoscapes in The Netherlands. Spatial variations in 87Sr/86Sr as a proxy for palaeomobility

    NARCIS (Netherlands)

    Kootker, Lisette M.; van Lanen, Rowin J.; Kars, Henk; Davies, Gareth R.

    2016-01-01

    Strontium isotope analysis has been successfully applied to archaeological questions of residential mobility and animal husbandry for over three decades. To obtain a full understanding of variations in archaeological samples, spatial variations in bioavailable strontium should be accurately mapped o

  15. The quantitative modelling of human spatial habitability

    Science.gov (United States)

    Wise, James A.

    1988-01-01

    A theoretical model for evaluating human spatial habitability (HuSH) in the proposed U.S. Space Station is developed. Optimizing the fitness of the space station environment for human occupancy will help reduce environmental stress due to long-term isolation and confinement in its small habitable volume. The development of tools that operationalize the behavioral bases of spatial volume for visual kinesthetic, and social logic considerations is suggested. This report further calls for systematic scientific investigations of how much real and how much perceived volume people need in order to function normally and with minimal stress in space-based settings. The theoretical model presented in this report can be applied to any size or shape interior, at any scale of consideration, for the Space Station as a whole to an individual enclosure or work station. Using as a point of departure the Isovist model developed by Dr. Michael Benedikt of the U. of Texas, the report suggests that spatial habitability can become as amenable to careful assessment as engineering and life support concerns.

  16. Accommodating environmental variation in population models: metaphysiological biomass loss accounting.

    Science.gov (United States)

    Owen-Smith, Norman

    2011-07-01

    1. There is a pressing need for population models that can reliably predict responses to changing environmental conditions and diagnose the causes of variation in abundance in space as well as through time. In this 'how to' article, it is outlined how standard population models can be modified to accommodate environmental variation in a heuristically conducive way. This approach is based on metaphysiological modelling concepts linking populations within food web contexts and underlying behaviour governing resource selection. Using population biomass as the currency, population changes can be considered at fine temporal scales taking into account seasonal variation. Density feedbacks are generated through the seasonal depression of resources even in the absence of interference competition. 2. Examples described include (i) metaphysiological modifications of Lotka-Volterra equations for coupled consumer-resource dynamics, accommodating seasonal variation in resource quality as well as availability, resource-dependent mortality and additive predation, (ii) spatial variation in habitat suitability evident from the population abundance attained, taking into account resource heterogeneity and consumer choice using empirical data, (iii) accommodating population structure through the variable sensitivity of life-history stages to resource deficiencies, affecting susceptibility to oscillatory dynamics and (iv) expansion of density-dependent equations to accommodate various biomass losses reducing population growth rate below its potential, including reductions in reproductive outputs. Supporting computational code and parameter values are provided. 3. The essential features of metaphysiological population models include (i) the biomass currency enabling within-year dynamics to be represented appropriately, (ii) distinguishing various processes reducing population growth below its potential, (iii) structural consistency in the representation of interacting populations and

  17. Indoorgml - a Standard for Indoor Spatial Modeling

    Science.gov (United States)

    Li, Ki-Joune

    2016-06-01

    With recent progress of mobile devices and indoor positioning technologies, it becomes possible to provide location-based services in indoor space as well as outdoor space. It is in a seamless way between indoor and outdoor spaces or in an independent way only for indoor space. However, we cannot simply apply spatial models developed for outdoor space to indoor space due to their differences. For example, coordinate reference systems are employed to indicate a specific position in outdoor space, while the location in indoor space is rather specified by cell number such as room number. Unlike outdoor space, the distance between two points in indoor space is not determined by the length of the straight line but the constraints given by indoor components such as walls, stairs, and doors. For this reason, we need to establish a new framework for indoor space from fundamental theoretical basis, indoor spatial data models, and information systems to store, manage, and analyse indoor spatial data. In order to provide this framework, an international standard, called IndoorGML has been developed and published by OGC (Open Geospatial Consortium). This standard is based on a cellular notion of space, which considers an indoor space as a set of non-overlapping cells. It consists of two types of modules; core module and extension module. While core module consists of four basic conceptual and implementation modeling components (geometric model for cell, topology between cells, semantic model of cell, and multi-layered space model), extension modules may be defined on the top of the core module to support an application area. As the first version of the standard, we provide an extension for indoor navigation.

  18. [Spatial variation characteristics of surface soil water content, bulk density and saturated hydraulic conductivity on Karst slopes].

    Science.gov (United States)

    Zhang, Chuan; Chen, Hong-Song; Zhang, Wei; Nie, Yun-Peng; Ye, Ying-Ying; Wang, Ke-Lin

    2014-06-01

    Surface soil water-physical properties play a decisive role in the dynamics of deep soil water. Knowledge of their spatial variation is helpful in understanding the processes of rainfall infiltration and runoff generation, which will contribute to the reasonable utilization of soil water resources in mountainous areas. Based on a grid sampling scheme (10 m x 10 m) and geostatistical methods, this paper aimed to study the spatial variability of surface (0-10 cm) soil water content, soil bulk density and saturated hydraulic conductivity on a typical shrub slope (90 m x 120 m, projected length) in Karst area of northwest Guangxi, southwest China. The results showed that the surface soil water content, bulk density and saturated hydraulic conductivity had different spatial dependence and spatial structure. Sample variogram of the soil water content was fitted well by Gaussian models with the nugget effect, while soil bulk density and saturated hydraulic conductivity were fitted well by exponential models with the nugget effect. Variability of soil water content showed strong spatial dependence, while the soil bulk density and saturated hydraulic conductivity showed moderate spatial dependence. The spatial ranges of the soil water content and saturated hydraulic conductivity were small, while that of the soil bulk density was much bigger. In general, the soil water content increased with the increase of altitude while it was opposite for the soil bulk densi- ty. However, the soil saturated hydraulic conductivity had a random distribution of large amounts of small patches, showing high spatial heterogeneity. Soil water content negatively (P conductivity, while there was no significant correlation between the soil bulk density and saturated hydraulic conductivity.

  19. Isard's contributions to spatial interaction modeling

    Science.gov (United States)

    O'Kelly, M. E.

    . This short review, surveys Isard's role in promoting what has become known as spatial interaction modeling. Some contextual information on the milieu from which his work emerged is given, together with a selected number of works that are judged to have been influenced (directly and indirectly) by his work. It is suggested that this burgeoning field owes a lot to the foundations laid in the gravity model chapter of ``Methods''. The review is supplemented by a rather extensive bibliography of additional works that are indicative of the breadth of the impact of this field.

  20. Spatial variation in the power of mountain streams in the Sangre de Cristo Mountains, New Mexico

    Science.gov (United States)

    Fonstad, Mark A.

    2003-09-01

    The principle indicator of river energy expenditure, stream power, has a significant influence on many forms and process attributes of the fluvial system, yet few basin-wide analyses of stream power variations have ever been conducted. Recent studies hypothesize a peak in the mean stream power distribution in small (10 km 2)- to intermediate (100 km 2)-sized basins. To test hypothetical stream power profiles in a high mountain setting, 129 cross-sections of stream networks within the Costilla basin of northern New Mexico and southern Colorado were measured for channel form, local sediment conditions, and basin characteristics. Geomorphic and hydrologic analysis of these river sites throughout the Costilla basin yielded evidence of abundant local control over fluvial processes and forms. Within the basin, the spatial deviations of stream power from the hypothetical patterns derived from hydraulic geometry, in some cases >200% deviation, match areas of specific geologic and hydrogeologic control. As an alternative to traditional hydraulic descriptions of downstream channel form, a probabilistic process-response model can incorporate local and basin-scale variables and allow more realistic feedback mechanisms than in traditional regime theory. The probabilistic nature of this type of model also allows prediction of multiple modes of channel adjustment, an ever-present challenge to extremal and physically based simulations.

  1. Patterns of Spatial Variation of Assemblages Associated with Intertidal Rocky Shores: A Global Perspective

    Science.gov (United States)

    Cruz-Motta, Juan José; Miloslavich, Patricia; Palomo, Gabriela; Iken, Katrin; Konar, Brenda; Pohle, Gerhard; Trott, Tom; Benedetti-Cecchi, Lisandro; Herrera, César; Hernández, Alejandra; Sardi, Adriana; Bueno, Andrea; Castillo, Julio; Klein, Eduardo; Guerra-Castro, Edlin; Gobin, Judith; Gómez, Diana Isabel; Riosmena-Rodríguez, Rafael; Mead, Angela; Bigatti, Gregorio; Knowlton, Ann; Shirayama, Yoshihisa

    2010-01-01

    Assemblages associated with intertidal rocky shores were examined for large scale distribution patterns with specific emphasis on identifying latitudinal trends of species richness and taxonomic distinctiveness. Seventy-two sites distributed around the globe were evaluated following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org). There were no clear patterns of standardized estimators of species richness along latitudinal gradients or among Large Marine Ecosystems (LMEs); however, a strong latitudinal gradient in taxonomic composition (i.e., proportion of different taxonomic groups in a given sample) was observed. Environmental variables related to natural influences were strongly related to the distribution patterns of the assemblages on the LME scale, particularly photoperiod, sea surface temperature (SST) and rainfall. In contrast, no environmental variables directly associated with human influences (with the exception of the inorganic pollution index) were related to assemblage patterns among LMEs. Correlations of the natural assemblages with either latitudinal gradients or environmental variables were equally strong suggesting that neither neutral models nor models based solely on environmental variables sufficiently explain spatial variation of these assemblages at a global scale. Despite the data shortcomings in this study (e.g., unbalanced sample distribution), we show the importance of generating biological global databases for the use in large-scale diversity comparisons of rocky intertidal assemblages to stimulate continued sampling and analyses. PMID:21179546

  2. Estimation of Spatial Dynamic Nonparametric Durbin Models with Fixed Effects

    Science.gov (United States)

    Qian, Minghui; Hu, Ridong; Chen, Jianwei

    2016-01-01

    Spatial panel data models have been widely studied and applied in both scientific and social science disciplines, especially in the analysis of spatial influence. In this paper, we consider the spatial dynamic nonparametric Durbin model (SDNDM) with fixed effects, which takes the nonlinear factors into account base on the spatial dynamic panel…

  3. Modeling the climatic response to orbital variations.

    Science.gov (United States)

    Imbrie, J; Imbrie, J Z

    1980-02-29

    According to the astronomical theory of climate, variations in the earth's orbit are the fundamental cause of the succession of Pleistocene ice ages. This article summarizes how the theory has evolved since the pioneer studies of James Croll and Milutin Milankovitch, reviews recent evidence that supports the theory, and argues that a major opportunity is at hand to investigate the physical mechanisms by which the climate system responds to orbital forcing. After a survey of the kinds of models that have been applied to this problem, a strategy is suggested for building simple, physically motivated models, and a time-dependent model is developed that simulates the history of planetary glaciation for the past 500,000 years. Ignoring anthropogenic and other possible sources of variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-term cooling trend which began some 6000 years ago will continue for the next 23,000 years.

  4. The quantitative modelling of human spatial habitability

    Science.gov (United States)

    Wise, J. A.

    1985-01-01

    A model for the quantitative assessment of human spatial habitability is presented in the space station context. The visual aspect assesses how interior spaces appear to the inhabitants. This aspect concerns criteria such as sensed spaciousness and the affective (emotional) connotations of settings' appearances. The kinesthetic aspect evaluates the available space in terms of its suitability to accommodate human movement patterns, as well as the postural and anthrometric changes due to microgravity. Finally, social logic concerns how the volume and geometry of available space either affirms or contravenes established social and organizational expectations for spatial arrangements. Here, the criteria include privacy, status, social power, and proxemics (the uses of space as a medium of social communication).

  5. Modeling the spatial reach of the LFP.

    Science.gov (United States)

    Lindén, Henrik; Tetzlaff, Tom; Potjans, Tobias C; Pettersen, Klas H; Grün, Sonja; Diesmann, Markus; Einevoll, Gaute T

    2011-12-08

    The local field potential (LFP) reflects activity of many neurons in the vicinity of the recording electrode and is therefore useful for studying local network dynamics. Much of the nature of the LFP is, however, still unknown. There are, for instance, contradicting reports on the spatial extent of the region generating the LFP. Here, we use a detailed biophysical modeling approach to investigate the size of the contributing region by simulating the LFP from a large number of neurons around the electrode. We find that the size of the generating region depends on the neuron morphology, the synapse distribution, and the correlation in synaptic activity. For uncorrelated activity, the LFP represents cells in a small region (within a radius of a few hundred micrometers). If the LFP contributions from different cells are correlated, the size of the generating region is determined by the spatial extent of the correlated activity.

  6. Geomagnetic Core Field Secular Variation Models

    DEFF Research Database (Denmark)

    Gillet, N.; Lesur, V.; Olsen, Nils

    2010-01-01

    We analyse models describing time changes of the Earth’s core magnetic field (secular variation) covering the historical period (several centuries) and the more recent satellite era (previous decade), and we illustrate how both the information contained in the data and the a priori information...... highlight the difficulty of resolving the time variability of the high degree secular variation coefficients (i.e. the secular acceleration), arising for instance from the challenge to properly separate sources of internal and of external origin. In addition, the regularisation process may also result...

  7. Methane variations on orbital timescales: a transient modeling experiment

    Directory of Open Access Journals (Sweden)

    T. Y. M. Konijnendijk

    2011-06-01

    Full Text Available Methane (CH4 variations on orbital timescales are often associated with variations in wetland coverage, most notably in the summer monsoon areas of the Northern Hemisphere. Here we test this assumption by simulating orbitally forced variations in global wetland emissions, using a simple wetland distribution and CH4 emissions model that has been run on the output of a climate model (CLIMBER-2 containing atmosphere, ocean and vegetation components. The transient climate modeling simulation extends over the last 650 000 yr and includes variations in land-ice distribution and greenhouse gases. Tropical temperature and global vegetation are found to be the dominant controls for global CH4 emissions and therefore atmospheric concentrations. The relative importance of wetland coverage, vegetation coverage, and emission temperatures depends on the specific climatic zone (boreal, tropics and Indian/Asian monsoon area and timescale (precession, obliquity and glacial-interglacial timescales. Despite the low spatial resolution of the climate model and crude parameterizations for methane production and release, simulated variations in CH4 emissions agree well with those in measured concentrations, both in their time series and spectra. The simulated lags between emissions and orbital forcing also show close agreement with those found in measured data, both on the precession and obliquity timescale. We find causal links between atmospheric CH4 concentrations and tropical temperatures and global vegetation, but only covariance between monsoon precipitation and CH4 concentrations. The primary importance of the first two factors explains the lags found in the CH4 record from ice cores. Simulation of the dynamical vegetation response to climate variation on orbital timescales would be needed to reduce the uncertainty in these preliminary attributions.

  8. Spatial Database Modeling for Indoor Navigation Systems

    Science.gov (United States)

    Gotlib, Dariusz; Gnat, Miłosz

    2013-12-01

    For many years, cartographers are involved in designing GIS and navigation systems. Most GIS applications use the outdoor data. Increasingly, similar applications are used inside buildings. Therefore it is important to find the proper model of indoor spatial database. The development of indoor navigation systems should utilize advanced teleinformation, geoinformatics, geodetic and cartographical knowledge. The authors present the fundamental requirements for the indoor data model for navigation purposes. Presenting some of the solutions adopted in the world they emphasize that navigation applications require specific data to present the navigation routes in the right way. There is presented original solution for indoor data model created by authors on the basis of BISDM model. Its purpose is to expand the opportunities for use in indoor navigation.

  9. Spatial and Temporal Variation of Meteorological Drought in the Parambikulam-Aliyar Basin, Tamil Nadu

    Science.gov (United States)

    Manikandan, M.; Tamilmani, D.

    2015-09-01

    The present study aims to investigate the spatial and temporal variation of meteorological drought in the Parambikulam-Aliyar basin, Tamil Nadu using the Standardized Precipitation Index (SPI) as an indicator of drought severity. The basin was divided into 97 grid-cells of 5 × 5 km with each grid correspondence to approximately 1.03 % of total area. Monthly rainfall data for the period of 40 years (1972-2011) from 28 rain gauge stations in the basin was spatially interpolated and gridded monthly rainfall was created. Regional representative of SPI values calculated from mean areal rainfall were used to analyse the temporal variation of drought at multiple time scales. Spatial variation of drought was analysed based on highest drought severity derived from the monthly gridded SPI values. Frequency analyse was applied to assess the recurrence pattern of drought severity. The temporal analysis of SPI indicated that moderate, severe and extreme droughts are common in the basin and spatial analysis of drought severity identified the areas most frequently affected by drought. The results of this study can be used for developing drought preparedness plan and formulating mitigation strategies for sustainable water resource management within the basin.

  10. Role of malnutrition and parasite infections in the spatial variation in children's anaemia risk in northern Angola.

    Science.gov (United States)

    Soares Magalhães, Ricardo J; Langa, Antonio; Pedro, João Mário; Sousa-Figueiredo, José Carlos; Clements, Archie C A; Vaz Nery, Susana

    2013-05-01

    Anaemia is known to have an impact on child development and mortality and is a severe public health problem in most countries in sub-Saharan Africa. We investigated the consistency between ecological and individual-level approaches to anaemia mapping by building spatial anaemia models for children aged ≤15 years using different modelling approaches. We aimed to (i) quantify the role of malnutrition, malaria, Schistosoma haematobium and soil-transmitted helminths (STHs) in anaemia endemicity; and (ii) develop a high resolution predictive risk map of anaemia for the municipality of Dande in northern Angola. We used parasitological survey data for children aged ≤15 years to build Bayesian geostatistical models of malaria (PfPR≤15), S. haematobium, Ascaris lumbricoides and Trichuris trichiura and predict small-scale spatial variations in these infections. Malnutrition, PfPR≤15, and S. haematobium infections were significantly associated with anaemia risk. An estimated 12.5%, 15.6% and 9.8% of anaemia cases could be averted by treating malnutrition, malaria and S. haematobium, respectively. Spatial clusters of high risk of anaemia (>86%) were identified. Using an individual-level approach to anaemia mapping at a small spatial scale, we found that anaemia in children aged ≤15 years is highly heterogeneous and that malnutrition and parasitic infections are important contributors to the spatial variation in anaemia risk. The results presented in this study can help inform the integration of the current provincial malaria control programme with ancillary micronutrient supplementation and control of neglected tropical diseases such as urogenital schistosomiasis and STH infections.

  11. Role of malnutrition and parasite infections in the spatial variation in children’s anaemia risk in northern Angola

    Directory of Open Access Journals (Sweden)

    Ricardo J. Soares Magalhães

    2013-05-01

    Full Text Available Anaemia is known to have an impact on child development and mortality and is a severe public health problem in most countries in sub-Saharan Africa. We investigated the consistency between ecological and individual-level approaches to anaemia mapping by building spatial anaemia models for children aged ≤15 years using different modelling approaches. We aimed to (i quantify the role of malnutrition, malaria, Schistosoma haematobium and soil-transmitted helminths (STHs in anaemia endemicity; and (ii develop a high resolution predictive risk map of anaemia for the municipality of Dande in northern Angola. We used parasitological survey data for children aged ≤15 years to build Bayesian geostatistical models of malaria (PfPR≤15, S. haematobium, Ascaris lumbricoides and Trichuris trichiura and predict small-scale spatial variations in these infections. Malnutrition, PfPR≤15, and S. haematobium infections were significantly associated with anaemia risk. An estimated 12.5%, 15.6% and 9.8% of anaemia cases could be averted by treating malnutrition, malaria and S. haematobium, respectively. Spatial clusters of high risk of anaemia (>86% were identified. Using an individual-level approach to anaemia mapping at a small spatial scale, we found that anaemia in children aged ≤15 years is highly heterogeneous and that malnutrition and parasitic infections are important contributors to the spatial variation in anaemia risk. The results presented in this study can help inform the integration of the current provincial malaria control programme with ancillary micronutrient supplementation and control of neglected tropical diseases such as urogenital schistosomiasis and STH infections.

  12. Spatially varying coefficient models in real estate: Eigenvector spatial filtering and alternative approaches

    NARCIS (Netherlands)

    Helbich, M; Griffith, D

    2016-01-01

    Real estate policies in urban areas require the recognition of spatial heterogeneity in housing prices to account for local settings. In response to the growing number of spatially varying coefficient models in housing applications, this study evaluated four models in terms of their spatial patterns

  13. The spatial coefficient of variation in arterial spin labeling cerebral blood flow images.

    Science.gov (United States)

    Mutsaerts, Henri Jmm; Petr, Jan; Václavů, Lena; van Dalen, Jan W; Robertson, Andrew D; Caan, Matthan W; Masellis, Mario; Nederveen, Aart J; Richard, Edo; MacIntosh, Bradley J

    2017-09-01

    Macro-vascular artifacts are a common arterial spin labeling (ASL) finding in populations with prolonged arterial transit time (ATT) and result in vascular regions with spuriously increased cerebral blood flow (CBF) and tissue regions with spuriously decreased CBF. This study investigates whether there is an association between the spatial signal distribution of a single post-label delay ASL CBF image and ATT. In 186 elderly with hypertension (46% male, 77.4 ± 2.5 years), we evaluated associations between the spatial coefficient of variation (CoV) of a CBF image and ATT. The spatial CoV and ATT metrics were subsequently evaluated with respect to their associations with age and sex - two demographics known to influence perfusion. Bland-Altman plots showed that spatial CoV predicted ATT with a maximum relative error of 7.6%. Spatial CoV was associated with age (β = 0.163, p = 0.028) and sex (β = -0.204, p = 0.004). The spatial distribution of the ASL signal on a standard CBF image can be used to infer between-participant ATT differences. In the absence of ATT mapping, the spatial CoV may be useful for the clinical interpretation of ASL in patients with cerebrovascular pathology that leads to prolonged transit of the ASL signal to tissue.

  14. A Computational Model of Spatial Development

    Science.gov (United States)

    Hiraki, Kazuo; Sashima, Akio; Phillips, Steven

    Psychological experiments on children's development of spatial knowledge suggest experience at self-locomotion with visual tracking as important factors. Yet, the mechanism underlying development is unknown. We propose a robot that learns to mentally track a target object (i.e., maintaining a representation of an object's position when outside the field-of-view) as a model for spatial development. Mental tracking is considered as prediction of an object's position given the previous environmental state and motor commands, and the current environment state resulting from movement. Following Jordan & Rumelhart's (1992) forward modeling architecture the system consists of two components: an inverse model of sensory input to desired motor commands; and a forward model of motor commands to desired sensory input (goals). The robot was tested on the `three cups' paradigm (where children are required to select the cup containing the hidden object under various movement conditions). Consistent with child development, without the capacity for self-locomotion the robot's errors are self-center based. When given the ability of self-locomotion the robot responds allocentrically.

  15. Spatial Economics Model Predicting Transport Volume

    Directory of Open Access Journals (Sweden)

    Lu Bo

    2016-10-01

    Full Text Available It is extremely important to predict the logistics requirements in a scientific and rational way. However, in recent years, the improvement effect on the prediction method is not very significant and the traditional statistical prediction method has the defects of low precision and poor interpretation of the prediction model, which cannot only guarantee the generalization ability of the prediction model theoretically, but also cannot explain the models effectively. Therefore, in combination with the theories of the spatial economics, industrial economics, and neo-classical economics, taking city of Zhuanghe as the research object, the study identifies the leading industry that can produce a large number of cargoes, and further predicts the static logistics generation of the Zhuanghe and hinterlands. By integrating various factors that can affect the regional logistics requirements, this study established a logistics requirements potential model from the aspect of spatial economic principles, and expanded the way of logistics requirements prediction from the single statistical principles to an new area of special and regional economics.

  16. Ontogenetic, spatial and temporal variation in trophic level and diet of Chukchi Sea fishes

    Science.gov (United States)

    Marsh, Jennifer M.; Mueter, Franz J.; Iken, Katrin; Danielson, Seth

    2017-01-01

    Climate warming and increasing development are expected to alter the ecosystem of the Chukchi Sea, including its fish communities. As a component of the Arctic Ecosystem Integrated Survey, we assessed the ontogenetic, spatial and temporal variability of the trophic level and diet of key fish species in the Chukchi Sea using N and C stable isotopes. During August and September of 2012 and 2013, 16 common fish species and two primary, invertebrate consumers were collected from surface, midwater and bottom trawls within the eastern Chukchi Sea. Linear mixed-effects models were used to detect possible variation in the relationship between body length and either δ13C or δ15N values among water masses and years for 13 fish species with an emphasis on Arctic cod (Boreogadus saida). We also examined the fish community isotopic niche space, trophic redundancy, and trophic separation within each water mass as measures of resiliency of the fish food web. Ontogenetic shifts in trophic level and diet were observed for most species and these changes tended to vary by water mass. As they increased in length, most fish species relied more on benthic prey with the exception of three forage fish species (walleye pollock, Gadus chalcogrammus, capelin, Mallotus villosus, and Pacific sandlance, Ammodytes hexapterus). Species that exhibited interannual differences in diet and trophic level were feeding at lower trophic levels and consumed a more pelagic diet in 2012 when zooplankton densities were higher. Fish communities occupied different isotopic niche spaces depending on water mass association. In more northerly Arctic waters, the fish community occupied the smallest isotopic niche space and relied heavily on a limited range of intermediate δ13C prey, whereas in warmer, nutrient-rich Bering Chukchi Summer Water, pelagic prey was important. In the warmest, Pacific-derived coastal water, fish consumed both benthic and pelagic prey. Examining how spatial gradients in trophic

  17. Model of light variations of Be stars

    Energy Technology Data Exchange (ETDEWEB)

    Stepinski, T. (Polska Akademia Nauk, Warsaw. Centrum Astronomiczne)

    1980-01-01

    The following model of Be star is proposed: a star rotating rigidly with a ''break up'' velocity is surrounded with a flat, geometrically thin, optically thick gaseous disk rotating with a Keplerian velocity. The disk absorbs and reemits stellar light. Viscous heat dissipation in the disk is neglected. The emerging spectrum of the system is calculated in black body approximation with temperature being a function of a position on the star and on the disk. Variation of the inner and outer disk radii may give rise to monochromatic light variations of the whole system in the range of 0.1-0.7 magnitudes. The light variations observed in Be stars are in the same range.

  18. Variational modelling of nonlinear water waves

    Science.gov (United States)

    Kalogirou, Anna; Bokhove, Onno

    2015-11-01

    Mathematical modelling of water waves is demonstrated by investigating variational methods. A potential flow water wave model is derived using variational techniques and extented to include explicit time-dependence, leading to non-autonomous dynamics. As a first example, we consider the problem of a soliton splash in a long wave channel with a contraction at its end, resulting after a sluice gate is removed at a finite time. The removal of the sluice gate is included in the variational principle through a time-dependent gravitational potential. A second example involving non-autonomous dynamics concerns the motion of a free surface in a vertical Hele-Shaw cell. Explicit time-dependence now enters the model through a linear damping term due to the effect of wall friction and a term representing the motion of an artificially driven wave pump. In both cases, the model is solved numerically using a Galerkin FEM and the numerical results are compared to wave structures observed in experiments. The water wave model is also adapted to accommodate nonlinear ship dynamics. The novelty is this case is the coupling between the water wave dynamics, the ship dynamics and water line dynamics on the ship. For simplicity, we consider a simple ship structure consisting of V-shaped cross-sections.

  19. Temporal-spatial variation and the influence factors of precipitation in Sichuan Province, China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Precipitation is a key factor in the water cycle.At the same time,precipitation is the focus of study in meteorology and climatology,ecological environmental assessment,non-point source pollution and so on.Understanding the temporal-spatial variation and the corresponding factors of precipitation has become the object of hydrology and environmentology.Based on the annual precipitation data,we analyzed the spatial distribution of precipitation in Sichuan Province in China as well as the temporal-spatial variation and the corresponding influence factors involved.The results show that the amount of precipitation was abundant,but the spatial distribution was not consistent with it and the amount of precipitation gradually declined from the south-east to the north-west in Sichuan Province,China.Moreover,the spatial distribution was different throughout the years.The result of correlation analysis indicated that elevation,temperature and air pressure were three key factors affecting the amount and distribution of precipitation,and the correlation coefficients were -0.56,0.38 and 0.45 respectively.Notably,the relationship between the slope of topography and precipitation were significantly negative and the average correlation coefficient was -0.28.

  20. Spatial variation in rates of carbon and nitrogen accumulation in a boreal bog

    Energy Technology Data Exchange (ETDEWEB)

    Ohlson, M. [Agricultural Univ. of Norway, Aas (Norway). Dept. of Biology and Nature Conservation; Oekland, R.H. [Univ. of Oslo (Norway)

    1998-12-01

    Although previous studies hint at the occurrence of substantial spatial variation in the accumulation rates of C and N in bogs, the extent to which rates may vary on high-resolution spatial and temporal scales is not known. A main reason for the lack of knowledge is that it is problematic to determine the precise age of peat at a given depth. The authors determined rates of carbon and nitrogen accumulation in the uppermost decimeters of a bog ecosystem using the pine method, which enables accurate dating of surface peat layers. They combined accumulation data with numerical and geostatistical analyses of the recent vegetation to establish the relationship between bog vegetation and rate of peat accumulation. Use of a laser technique for spatial positioning of 151 age-determined peat cores within a 20 x 20 m plot made it possible to give the first tine-scaled account of spatial and temporal variation in rates of mass, carbon, and nitrogen accumulation during the last century. Rates of C and N accumulation were highly variable at all spatial scales studied. For example, after {approximately}125 yr of peat growth, C and N accumulation varied by factors of five and four, respectively, from 25 to 125 g/dm{sup 2} for C, and from 0.7 to 2.6 g/dm{sup 2} for N. It takes 40 yr of peat accumulation before significant amounts of C are lost through decay. Hummocks built up by Sphagnum fuscum and S. rubellum were able to maintain average rates of C accumulation that exceed 2 g{center_dot}dm{sup {minus}2}{center_dot} yr{sup {minus}1} during 50 yr of growth. The authors argue that data on spatial variation in rates of C accumulation are necessary to understand the role of boreal peatlands in the greenhouse effect and global climate.

  1. Spatial Variation of the Foil Parameters from in Situ Calibration of the JT-60U Imaging Bolometer Foil

    Science.gov (United States)

    Araghy, Homaira P.; Peterson, Byron J.; Hayashi, Hiromi; Konoshima, Shigeru; Ashikawa, Naoko; Seo, Dongcheol; JT-60U Team

    We obtained the local foil properties of the JT-60U imaging bolometer foil (a single graphite-coated gold foil with an effective area of 9 × 7 cm2 and a nominal thickness of 2.5 μm) such as the thermal diffusivity, κ, and the product of the thermal conductivity, k, and the thickness, tf , by calibrating some parts of the foil. Calibration of the foil was made in situ using a He-Ne laser (˜27 mW) as a known radiation source to heat the foil. The thermal images of the foil are provided by an infrared (IR) camera (microbolometer type). The parameters are determined by finite element modeling (FEM) of the foil temperature and comparing the solution to the experimental results. In this work we apply this calibration technique to investigate the spatial variation of the foil parameters. Significant variation in the local temperature rise of the foil due to local heating by the laser beam indicates a spatial variation of the foil parameters κ, k and tf. This variation is possibly due to nonuniformity in carbon coating and/or the thickness of the foil.

  2. The importance of spatial variation of benthic invertebrates for the ecological assessment of European lakes

    DEFF Research Database (Denmark)

    Solimini, Angelo G.; Sandin, Leif Leonard

    2012-01-01

    at multiple spatial scales needs to be assessed and efficiently quantified, in order to set up reliable assessment tools of ecological status. Driven by the research activity carried out within the European project Wiser (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery......Lake assessment systems based on benthic macroinvertebrates critically depend on the amount of spatial variation of organisms within and between lakes. Investigators need to distinguish between community changes that are related to human pressures and those that are caused by inherent natural...

  3. Spatial and temporal variation of historical anthropogenic NMVOCs emission inventories in China

    Directory of Open Access Journals (Sweden)

    Y. Bo

    2008-12-01

    Full Text Available Multiyear emission inventories of anthropogenic NMVOCs in China for 1980–2005 were established based on time-varying statistical data, literature surveyed and model calculated emission factors, which were further gridded at a high spatial resolution of 40 km×40 km using the GIS methodology. Results show a continuous growth trend of China's historical NMVOCs emissions during the period of 1980–2005, with the emission increasing by 4.2 times at an annual average rate of 10.6% from 3.91 Tg in 1980 to 16.49 Tg in 2005. Vehicles, biomass burning, industrial processes, fossil fuel combustion, solvent utilization, and storage and transport generated 5.50 Tg, 3.84 Tg, 2.76 Tg, 1.98 Tg, 1.87 Tg, and 0.55 Tg of NMVOCs, respectively, in 2005. Motorcycles, biofuel burning, heavy duty vans, synthetic fibre production, biomass open burning, and industrial and commercial consumption were primary emission sources. Besides, source contributions of NMVOCs emissions showed remarkable annual variation. However, emissions of these sources had been continuously increasing, which coincided well with China's economic growth. Spatial distribution of NMVOCs emissions illustrates that high emissions mainly concentrates in developed regions of northern, eastern and southern coastal areas, which produced more emissions than the relatively underdeveloped western and inland regions. Particularly, southeastern, northern, and central China covering 35.2% of China's territory, generated 59.4% of the total emissions, while the populous capital cities covering merely 4.5% of China's territory, accounted for 24.9% of the national emissions. Annual variation of regional emission intensity shows that emissions concentrating in urban areas tended to transfer to rural areas year by year. Moreover, eastern, southern, central, and northeastern China were typical areas of high emission intensity and had a tendency of expanding to the northwestern China, which

  4. Spatial and temporal variation of particulate matter and gaseous pollutants in China during 2014-2016

    Science.gov (United States)

    Li, Rui; Cui, Lulu; Li, Junlin; Zhao, An; Fu, Hongbo; Wu, Yu; Zhang, Liwu; Kong, Lingdong; Chen, Jianmin

    2017-07-01

    China is experiencing severe air pollution due to rapid economic development and accelerated urbanization. High-resolution temporal and spatial air pollution data are imperative to understand the physical and chemical processes affecting air quality of China. The data of PM2.5, PM10, SO2, CO, NO2, and O3 in 187 Chinese cities during January 2014 and November 2016 were collected to uncover the spatial and temporal variation of the pollutants in China. The annual mean concentrations of PM2.5 exceeded the Grade I standard of Chinese Ambient Air Quality (CAAQS) for all of the cities except several cities in Hainan, and more than 100 cities exceeded the CAAQS Grade II standard. The concentrations of PM2.5, PM10, SO2, CO, and NO2 decreased from 2014 to 2016, whereas the O3 level increased dramatically during this period. The concentrations of PM2.5, PM10, SO2, CO and NO2 exhibited the highest levels in winter and the lowest in summer, and evidently decreased from 2014 to 2016, whereas the O3 concentration peaked in spring and summer, and dramatically increased from 2014 to 2016. The non-attainment ratios were highest in winters, while high pollution days were also frequently observed in the Southeast region in autumn and in the Northwest region in spring. Pearson correlation analysis indicated that all of the pollutants exhibited significant correlation one another. PM10 was a major pollutant affecting the air quality of China in all of the seasons. Both SO2 and NO2 exerted significantly adverse effects on the air quality in spring and autumn, but CO played an important role on the air quality in winter. O3 was found to be the dominant species among the pollutants affecting the air quality in summer, suggesting that photochemical O3 formation should be paid more attention to improve the air quality in summer. The results of geographical weight regression (GWR) showed that more significant correlations among the pollutants and the highest air quality index (AQI) appeared

  5. Discrete Variational Approach for Modeling Laser-Plasma Interactions

    Science.gov (United States)

    Reyes, J. Paxon; Shadwick, B. A.

    2014-10-01

    The traditional approach for fluid models of laser-plasma interactions begins by approximating fields and derivatives on a grid in space and time, leading to difference equations that are manipulated to create a time-advance algorithm. In contrast, by introducing the spatial discretization at the level of the action, the resulting Euler-Lagrange equations have particular differencing approximations that will exactly satisfy discrete versions of the relevant conservation laws. For example, applying a spatial discretization in the Lagrangian density leads to continuous-time, discrete-space equations and exact energy conservation regardless of the spatial grid resolution. We compare the results of two discrete variational methods using the variational principles from Chen and Sudan and Brizard. Since the fluid system conserves energy and momentum, the relative errors in these conserved quantities are well-motivated physically as figures of merit for a particular method. This work was supported by the U. S. Department of Energy under Contract No. DE-SC0008382 and by the National Science Foundation under Contract No. PHY-1104683.

  6. Ecological and evolutionary consequences of tri-trophic interactions: Spatial variation and effects of plant density.

    Science.gov (United States)

    Abdala-Roberts, Luis; Parra-Tabla, Víctor; Moreira, Xoaquín; Ramos-Zapata, José

    2017-02-01

    The factors driving variation in species interactions are often unknown, and few studies have made a link between changes in interactions and the strength of selection. We report on spatial variation in functional responses by a seed predator (SP) and its parasitic wasps associated with the herb Ruellia nudiflora. We assessed the influence of plant density on consumer responses and determined whether density effects and spatial variation in functional responses altered natural selection by these consumers on the plant. We established common gardens at two sites in Yucatan, Mexico, and planted R. nudiflora at two densities in each garden. We recorded fruit output and SP and parasitoid attack; calculated relative fitness (seed number) under scenarios of three trophic levels (accounting for SP and parasitoid effects), two trophic levels (accounting for SP but not parasitoid effects), and one trophic level (no consumer effects); and compared selection strength on fruit number under these scenarios across sites and densities. There was spatial variation in SP recruitment, whereby the SP functional response was negatively density-dependent at one site but density-independent at the other; parasitoid responses were density-independent and invariant across sites. Site variation in SP attack led, in turn, to differences in SP selection on fruit output, and parasitoids did not alter SP selection. There were no significant effects of density at either site. Our results provide a link between consumer functional responses and consumer selection on plants, which deepens our understanding of geographic variation in the evolutionary outcomes of multitrophic interactions. © 2017 Botanical Society of America.

  7. Temporal and spatial variation of arbuscular mycorrhizas in salt marsh plants of the Tagus estuary (Portugal).

    Science.gov (United States)

    Carvalho, L M; Caçador, I; Martins-Loução, M

    2001-12-01

    The factors which may influence temporal and spatial variation in plant arbuscular mycorrhizal (AM) colonization and propagule occurrence were evaluated in a Portuguese salt marsh poor in plant diversity. Two distinct sites were studied: a more-flooded (low marsh) and a less-flooded zone (high marsh). AM root colonization, AM fungal spore number and inoculum potential, soil edaphic parameters and tidal flooding time periods were analysed. Levels of AM colonization were considerable in Aster tripolium and Inula crithmoides but very low in Puccinellia maritima and non-existent in Spartina maritima, Halimione portulacoides, Arthrocnemum fruticosum and Arthrocnemum perenne. Fungal diversity was very low, with Glomus geosporum dominant at both marsh zones. Colonization showed no spatial variation within marsh zones but temporal variation was observed in the high marsh, dependent on plant phenological phases. In the low marsh, no significantly seasonal variation was observed. Apparently, plant phenological events were diluted by stressful conditions (e.g. flooding, salinity). Spore density was significantly different between marsh zones and showed temporal variation in both zones. This study showed that distribution of mycorrhizas in salt marsh is more dependent on host plant species than on environmental stresses.

  8. Regional frequency analysis to asses wind resource spatial and temporal variations in Washington State

    Science.gov (United States)

    Mortuza, M.; Demissie, D.

    2013-12-01

    According to the U.S. Department of Energy's annual wind technologies market report, the wind power capacity in the country grew from 2.5 gigawatts in early 2000 to 60 gigawatts in 2012, making it one of the largest new sources of electric capacity additions in the U.S. in recent years. With over 2.8 gigawatts of current capacity (eighth largest in the nation), Washington State plays a significant role in this rapidly increasing energy resource. To further expand and/or optimize these capacities, assessment of wind resource and its spatial and temporal variations are important. However, since at-site frequency analysis using meteorological data is not adequate for extending wind frequency to locations with no data, longer return period, and heterogeneous topography and surface, a regional frequency analysis based on L-moment method is adopted in this study to estimate regional wind speed patterns and return periods in Washington State using hourly mean wind speed data from 1979 - 2010. The analysis applies the k-means, hierarchical and self-organizing map clustering techniques to explore potential clusters or regions; statistical tests are then applied to identify homogeneous regions and appropriate probability distribution models. The result from the analysis is expected to provide essential knowledge about the areas with potential capacity of constructing wind power plants, which can also be readily extended to assist decisions on their daily operations.

  9. An algorithm of multi-model spatial overlay based on three-dimensional terrain model TIN and its application

    Institute of Scientific and Technical Information of China (English)

    王少安; 张子平; 龚健雅

    2001-01-01

    3D-GIS spatial overlay analysis is being broadly concerned about in international academe and is a research focus. It is one of the important functions of spatial analysis using GIS technology. An algorithm of multi-model spatial overlay based on three-dimensional terrain model TIN is introduced in this paper which can be used to solve the TIN-based thrcc-dimensional overlay operation in spatial analysis. The feasibility arid validity of this algorithm is identified. This algorithm is used successfully in three-dimensional overlay and region variation overlay analysis.

  10. Variational multiscale models for charge transport.

    Science.gov (United States)

    Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin

    2012-01-01

    This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, meanwhile, dynamically couple discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to encompass the polar and nonpolar free energies of solvation, and chemical potential related energy. By using the Euler-Lagrange variation, coupled Laplace-Beltrami and Poisson-Nernst-Planck (LB-PNP) equations are derived. The solution of the LB-PNP equations leads to the minimization of the total free energy, and explicit profiles of electrostatic potential and densities of charge species. To further reduce the computational complexity, the Boltzmann distribution obtained from the Poisson-Boltzmann (PB) equation is utilized to represent the densities of certain charge species so as to avoid the computationally expensive solution of some Nernst-Planck (NP) equations. Consequently, the coupled Laplace-Beltrami and Poisson-Boltzmann-Nernst-Planck (LB-PBNP) equations are proposed for charge transport in heterogeneous systems. A major emphasis of the present formulation is the consistency between equilibrium LB-PB theory and non-equilibrium LB-PNP theory at equilibrium. Another major emphasis is the capability of the reduced LB-PBNP model to fully recover the prediction of the LB-PNP model at non-equilibrium settings. To account for the fluid impact on the charge transport, we derive coupled Laplace-Beltrami, Poisson-Nernst-Planck and Navier-Stokes equations from the variational principle

  11. Panel data models extended to spatial error autocorrelation or a spatially lagged dependent variable

    NARCIS (Netherlands)

    Elhorst, J. Paul

    2001-01-01

    This paper surveys panel data models extended to spatial error autocorrelation or a spatially lagged dependent variable. In particular, it focuses on the specification and estimation of four panel data models commonly used in applied research: the fixed effects model, the random effects model, the

  12. Spatial and temporal variations in the occurrence of low flow events in the UK

    Directory of Open Access Journals (Sweden)

    A. R. Young

    2000-01-01

    Full Text Available Information on the magnitude and variability of low river flows at the river reach scale is central to most aspects of water resource and water quality management. Within the UK, river stretches with permanent gauging stations represent less than one percent of the total number of river stretches mapped at a scale of 1:50,000 and fewer that 20% of gauged catchments can be regarded as having natural flow regimes. This has led to the development of simple, multivariate models for predicting average annual natural flow duration statistics through relationships with catchment characteristics. One assumption within these models is that low flows occur at the same time at all points within a catchment, irrespective of the hydrogeological nature and climatic condition of the catchment. This paper discusses the implications of spatial variations in the timing of low flow events for this type of model. Differences in the timing of the mean day of occurrence of the annual Q95 flow in UK catchments can be identified with low flows occurring earlier in the year within impermeable dry catchments and later in the year for wet permeable catchments. However, any differences in the mean day of occurrence between different catchments are generally masked by the magnitude of the inter-year variability in the day of occurrence. From analysis of linear combinations of flow statistics from nearest-neighbour gauged catchments, the paper demonstrates that the assumption of temporal coherence of low flows will generally result in an under-estimate of Q95; these underestimates are more significant for pairs of impermeable catchments than for combinations of permeable catchments and impermeable-permeable catchments.

  13. Spatial and temporal variations in the occurrence of low flow events in the UK

    Science.gov (United States)

    Young, A. R.; Round, C. E.; Gustard, A.

    Information on the magnitude and variability of low river flows at the river reach scale is central to most aspects of water resource and water quality management. Within the UK, river stretches with permanent gauging stations represent less than one percent of the total number of river stretches mapped at a scale of 1:50,000 and fewer that 20% of gauged catchments can be regarded as having natural flow regimes. This has led to the development of simple, multivariate models for predicting average annual natural flow duration statistics through relationships with catchment characteristics. One assumption within these models is that low flows occur at the same time at all points within a catchment, irrespective of the hydrogeological nature and climatic condition of the catchment. This paper discusses the implications of spatial variations in the timing of low flow events for this type of model. Differences in the timing of the mean day of occurrence of the annual Q95 flow in UK catchments can be identified with low flows occurring earlier in the year within impermeable dry catchments and later in the year for wet permeable catchments. However, any differences in the mean day of occurrence between different catchments are generally masked by the magnitude of the inter-year variability in the day of occurrence. From analysis of linear combinations of flow statistics from nearest-neighbour gauged catchments, the paper demonstrates that the assumption of temporal coherence of low flows will generally result in an under-estimate of Q95; these underestimates are more significant for pairs of impermeable catchments than for combinations of permeable catchments and impermeable-permeable catchments.

  14. High spatial variation in terrestrial arthropod species diversity and composition near the Greenland ice cap

    DEFF Research Database (Denmark)

    Hansen, Rikke Reisner; Hansen, Oskar Liset Pryds; Bowden, Joseph James;

    2016-01-01

    . The empirical basis for this assumption, however, is weak. We examine the degree of spatial variation in species diversity and assemblage structure among five habitat types at two sites of similar abiotic conditions and plant species composition in southwest Greenland, using standardized field collection...... drivers of local arthropod assemblages, we used a combination of ordination techniques and linear regression. Species richness and the species pool differed between sites, with the latter indicating high species turnover. Local-scale assemblage patterns were related to soil moisture and temperature. We......Arthropods form a major part of the terrestrial species diversity in the Arctic, and are particularly sensitive to temporal changes in the abiotic environment. It is assumed that most Arctic arthropods are habitat generalists and that their diversity patterns exhibit low spatial variation...

  15. Variation of spatial soliton in liquid crystals due change of polarization of the incident laser beam

    Science.gov (United States)

    Rodríguez-Rosales, A. A.; Román Moreno, C. J.; Ortega-Martínez, R.

    2013-11-01

    We present experimental evidence obtained in the generation and variation of dark to bright optical spatial solitons due the change of polarization plane of He-Ne laser beam incident in the sample of liquid crystals 5CB doped with methyl red at 0.1% wt inside a cell of 15 μm widths. This work is based in previous papers about the variation of nonlinear refraction index γ in liquid crystals, where we have demonstrated that under certain conditions it is possible to realize inversion of γ, from γ > 0 to γ system that will generate in the same material a controlled dark or bright spatial optical solitons. We consider this new phenomena very important and as well as its potential technological application in all-optical switching in telecommunications and optoelectronic.

  16. Metal accumulation in mosses across national boundaries: Uncovering and ranking causes of spatial variation

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Winfried [Landscape Ecology, University of Vechta, P.O. Box 1553, D-49364 Vechta (Germany)], E-mail: wschroeder@iuw.uni-vechta.de; Pesch, Roland [Landscape Ecology, University of Vechta, P.O. Box 1553, D-49364 Vechta (Germany)], E-mail: rpesch@iuw.uni-vechta.de; Englert, Cordula [Landscape Ecology, University of Vechta, P.O. Box 1553, D-49364 Vechta (Germany)], E-mail: cenglert@iuw.uni-vechta.de; Harmens, Harry [Centre for Ecology and Hydrology, Orton Building, Deiniol Road, Bangor, Gwynedd LL57 2UP (United Kingdom)], E-mail: hh@ceh.ac.uk; Suchara, Ivan [Silva Tarouca Research Institute for Landscape and Ornamental Gardening, Kvetnove namesti 391, CZ 252 43 Pruhonice, Cz-252 43 Pruhonice (Czech Republic)], E-mail: suchara@vukoz.cz; Zechmeister, Harald G. [Department of Conservation Biology, Vegetation- and Landscape Ecology, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna (Austria)], E-mail: harald.zechmeister@univie.ac.at; Thoeni, Lotti [FUB-Research Group for Environmental Monitoring, Untere Bahnhofstrasse 30, P.O. Box 1645, CH-8640 Rapperswil (Switzerland)], E-mail: lotti.thoeni@fub-ag.ch; Mankovska, Blanka [Institute of Landscape Ecology, Slovak Academy of Science, Stefanikova str. No. 3, P.O. Box 254, SK-814 99 Bratislava (Slovakia)], E-mail: bmankov@stonline.sk; Jeran, Zvonka [Department of Environmental Sciences, Institut Jozef Stefan, Jamova 39, 1000 Ljubljana (Slovenia)], E-mail: zvonka.jeran@ijs.si; Grodzinska, Krystyna [W. Szafer Institute of Botany, Polish Academy of Sciences, Lubicz 46, PL-31512 Krakow (Poland)], E-mail: grodzin@ib-pan.krakow.pl; Alber, Renate [Environmental Agency of Bolzano, Via Sottomonte 2, 39055 Laives (Italy)], E-mail: renate.alber@provinz.bz.it

    2008-01-15

    This study aimed at cross-border mapping metal loads in mosses in eight European countries in 1990, 1995, and 2000 and at investigating confounding factors. Geostatistics was used for mapping, indicating high local variances but clear spatial autocorrelations. Inference statistics identified differences of metal concentrations in mosses on both sides of the national borders. However, geostatistical analyses did not ascertain discontinuities of metal concentrations in mosses at national borders due to sample analysis in different laboratories applying a range of analytical techniques. Applying Classification and Regression Trees (CART) to the German moss data as an example, the local variation in metal concentrations in mosses were proved to depend mostly on different moss species, potential local emission sources, canopy drip and precipitation. - Factors affecting the spatial variation in metal accumulation in mosses were mapped by geostatistics and ranked by CART.

  17. Spatial variation of the magnetic field inside laminar flows of a perfect conductive fluid

    Science.gov (United States)

    Duka, Bejo; Boçi, Sonila

    2017-01-01

    The steady state of a perfect conductive fluid in laminar flow resulting from the ‘Hall effect’ is studied. Using the Maxwell equations, the spatial variation of the magnetic field in the steady state is calculated for three cases of different fluid flow geometries: flow between two infinite parallel planes, flow between two coaxial infinite-long cylinders and flow between two concentric spheres. According to our calculation of the three cases, the spatial variation of the magnetic field depends on the flow velocity. The magnetic field is strengthened in layers where the velocity is greater, but this dependency is negligible for non relativistic flows. Our approach in this study provides an example of how to receive interesting results using only basic knowledge of physics and mathematics.

  18. New Constraints on Spatial Variations of the Fine Structure Constant from Clusters of Galaxies

    Directory of Open Access Journals (Sweden)

    Ivan De Martino

    2016-12-01

    Full Text Available We have constrained the spatial variation of the fine structure constant using multi-frequency measurements of the thermal Sunyaev-Zeldovich effect of 618 X-ray selected clusters. Although our results are not competitive with the ones from quasar absorption lines, we improved by a factor 10 and ∼2.5 previous results from Cosmic Microwave Background power spectrum and from galaxy clusters, respectively.

  19. Spatial and Temporal Variation in Fungal Endophyte Communities Isolated from Cultivated Cotton (Gossypium hirsutum)

    OpenAIRE

    María J Ek-Ramos; Wenqing Zhou; Valencia, César U.; Antwi, Josephine B.; Kalns, Lauren L.; Gaylon D Morgan; David L. Kerns; Sword, Gregory A.

    2013-01-01

    Studies of fungi in upland cotton (Gossypium hirsutum) cultivated in the United States have largely focused on monitoring and controlling plant pathogens. Given increasing interest in asymptomatic fungal endophytes as potential biological control agents, surveys are needed to better characterize their diversity, distribution patterns and possible applications in integrated pest management. We sampled multiple varieties of cotton in Texas, USA and tested for temporal and spatial variation in f...

  20. Spatial Stochastic Point Models for Reservoir Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Syversveen, Anne Randi

    1997-12-31

    The main part of this thesis discusses stochastic modelling of geology in petroleum reservoirs. A marked point model is defined for objects against a background in a two-dimensional vertical cross section of the reservoir. The model handles conditioning on observations from more than one well for each object and contains interaction between objects, and the objects have the correct length distribution when penetrated by wells. The model is developed in a Bayesian setting. The model and the simulation algorithm are demonstrated by means of an example with simulated data. The thesis also deals with object recognition in image analysis, in a Bayesian framework, and with a special type of spatial Cox processes called log-Gaussian Cox processes. In these processes, the logarithm of the intensity function is a Gaussian process. The class of log-Gaussian Cox processes provides flexible models for clustering. The distribution of such a process is completely characterized by the intensity and the pair correlation function of the Cox process. 170 refs., 37 figs., 5 tabs.

  1. Modelling of the education quality of a high schools in Sumenep Regency using spatial structural equation modelling

    Science.gov (United States)

    Anekawati, Anik; Widjanarko Otok, Bambang; Purhadi; Sutikno

    2017-09-01

    In some cases, education research often involves the latent variables that have a causal relationship as well as a spatial effect. Therefore, it requires a statistical analysis technique called spatial structural equation modelling (spatial SEM). In this research, a spatial SEM was developed to model the quality of education in high schools in Sumenep Regency. This model was improved after the evaluation of an outer and inner model of the model scheme centroid, factor and path since some indicators were not valid. The path scheme model showed better results compared to the other schemes since all of its indicators were valid and its value of R-square increased. Furthermore, only the model of path scheme was tested for spatial effects. The result of the identification test of spatial effects on the inner model using a robust Lagrange multiplier test (using queen contiguity) showed that the education quality model leads to a spatial autoregressive model (SAR in SEM) with a significance level α of 5%, while the model of school infrastructure has no significant spatial effects. The improved model of SAR in SEM, the R2 value obtained was 47.33%, so that it is clear that data variation can be explained by the model of SAR in SEM for the quality of education in high schools.

  2. Effects of spatial variation in cohesion over the concrete-rock interface on dam sliding stability

    Institute of Scientific and Technical Information of China (English)

    Alexandra Krounis; Fredrik Johansson; Stefan Larsson

    2015-01-01

    The limit equilibrium method (LEM) is widely used for sliding stability evaluation of concrete gravity dams. Failure is then commonly assumed to occur along the entire sliding surface simultaneously. However, the brittle behaviour of bonded concrete-rock contacts, in combination with the varying stress over the interface, implies that the failure of bonded dam-foundation interfaces occurs progressively. In addition, the spatial variation in cohesion may introduce weak spots where failure can be initiated. Nonetheless, the combined effect of brittle failure and spatial variation in cohesion on the overall shear strength of the interface has not been studied previously. In this paper, numerical analyses are used to investigate the effect of brittle failure in combination with spatial variation in cohesion that is taken into account by random fields with different correlation lengths. The study concludes that a possible exis-tence of weak spots along the interface has to be considered since it significantly reduces the overall shear strength of the interface, and implications for doing so are discussed.

  3. Effects of spatial variation in cohesion over the concrete-rock interface on dam sliding stability

    Directory of Open Access Journals (Sweden)

    Alexandra Krounis

    2015-12-01

    Full Text Available The limit equilibrium method (LEM is widely used for sliding stability evaluation of concrete gravity dams. Failure is then commonly assumed to occur along the entire sliding surface simultaneously. However, the brittle behaviour of bonded concrete-rock contacts, in combination with the varying stress over the interface, implies that the failure of bonded dam-foundation interfaces occurs progressively. In addition, the spatial variation in cohesion may introduce weak spots where failure can be initiated. Nonetheless, the combined effect of brittle failure and spatial variation in cohesion on the overall shear strength of the interface has not been studied previously. In this paper, numerical analyses are used to investigate the effect of brittle failure in combination with spatial variation in cohesion that is taken into account by random fields with different correlation lengths. The study concludes that a possible existence of weak spots along the interface has to be considered since it significantly reduces the overall shear strength of the interface, and implications for doing so are discussed.

  4. Theoretical aspects of spatial-temporal modeling

    CERN Document Server

    Matsui, Tomoko

    2015-01-01

    This book provides a modern introductory tutorial on specialized theoretical aspects of spatial and temporal modeling. The areas covered involve a range of topics which reflect the diversity of this domain of research across a number of quantitative disciplines. For instance, the first chapter provides up-to-date coverage of particle association measures that underpin the theoretical properties of recently developed random set methods in space and time otherwise known as the class of probability hypothesis density framework (PHD filters). The second chapter gives an overview of recent advances in Monte Carlo methods for Bayesian filtering in high-dimensional spaces. In particular, the chapter explains how one may extend classical sequential Monte Carlo methods for filtering and static inference problems to high dimensions and big-data applications. The third chapter presents an overview of generalized families of processes that extend the class of Gaussian process models to heavy-tailed families known as alph...

  5. Spatial scales of variation in lichens: implications for sampling design in biomonitoring surveys.

    Science.gov (United States)

    Giordani, Paolo; Brunialti, Giorgio; Frati, Luisa; Incerti, Guido; Ianesch, Luca; Vallone, Emanuele; Bacaro, Giovanni; Maccherini, Simona

    2013-02-01

    The variability of biological data is a main constraint affecting the quality and reliability of lichen biomonitoring surveys for estimation of the effects of atmospheric pollution. Although most epiphytic lichen bioindication surveys focus on between-site differences at the landscape level, associated with the large scale effects of atmospheric pollution, current protocols are based on multilevel sampling, thus adding further sources of variation and affecting the error budget. We test the hypothesis that assemblages of lichen communities vary at each spatial scale examined, in order to determine what scales should be included in future monitoring studies. We compared four sites in Italy, along gradients of atmospheric pollution and climate, to test the partitioning of the variance components of lichen diversity across spatial scales (from trunks to landscapes). Despite environmental heterogeneity, we observed comparable spatial variance. However, residuals often overcame between-plot variability, leading to biased estimation of atmospheric pollution effects.

  6. Spatially-varying metric learning for diffeomorphic image registration: a variational framework.

    Science.gov (United States)

    Vialard, François-Xavier; Risser, Laurent

    2014-01-01

    This paper introduces a variational strategy to learn spatially-varying metrics on large groups of images, in the Large Deformation Diffeomorphic Metric Mapping (LDDMM) framework. Spatially-varying metrics we learn not only favor local deformations but also correlated deformations in different image regions and in different directions. In addition, metric parameters can be efficiently estimated using a gradient descent method. We first describe the general strategy and then show how to use it on 3D medical images with reasonable computational ressources. Our method is assessed on the 3D brain images of the LPBA40 dataset. Results are compared with ANTS-SyN and LDDMM with spatially-homogeneous metrics.

  7. Spatial and temporal variation of nitrogen exported by runoff from sandy agricultural soils

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The eutrophication problem has drawn attention to nutrient leaching from agricultural soils.and an understanding of spatial and temporal variability is needed to develop decision-making tools.Thus,eleven sites were selected to monitor,over a two-year period,spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils.Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed.Variation of annual rainfall was small among 11 situs.especially between 2001 and 2002.However,variation of annual discharge was significant among the sites.The results suggest that rainfall patterns and land usc had significant effect on discharge.The concentrations of total N,total kjeldahl N (TKN),organic matter-associated N (OM-N),NO3--N,and NH4+-N in the runoff ranged widely from 0.25 to 54.1,0.15 to 20.3,0.00 to 14.6,0.00 to 45.3,and 0.00 to 19.7 mg/L,respectively.Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites.Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge.High loads of total N,OM-N,NO3--N,and NH4+-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year,which coincided with the rainy season in the region.This study found that N in surface runoff was related to rainfall intensity,soil N level,and fertilizer use.

  8. Spatial and temporal variation of nitrogen exported by runoff from sandy agricultural soils.

    Science.gov (United States)

    Zhang, Ming-Kui; Wang, Li-Ping; He, Zhen-Li

    2007-01-01

    The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N (TKN), organic matter-associated N (OM-N), NO3(-)-N, and NH4(+)-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3(-)-N, and NH4(+)-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.

  9. Spatial variations of storm runoff pollution and their correlation with land-use in a rapidly urbanizing catchment in China.

    Science.gov (United States)

    Qin, Hua-Peng; Khu, Soon-Thiam; Yu, Xiang-Ying

    2010-09-15

    The composition of land use for a rapidly urbanizing catchment is usually heterogeneous, and this may result in significant spatial variations of storm runoff pollution and increase the difficulties of water quality management. The Shiyan Reservoir catchment, a typical rapidly urbanizing area in China, is chosen as a study area, and temporary monitoring sites were set at the downstream of its 6 sub-catchments to synchronously measure rainfall, runoff and water quality during 4 storm events in 2007 and 2009. Due to relatively low frequency monitoring, the IHACRES and exponential pollutant wash-off simulation models are used to interpolate the measured data to compensate for data insufficiency. Three indicators, event pollutant loads per unit area (EPL), event mean concentration (EMC) and pollutant loads transported by the first 50% of runoff volume (FF50), were used to describe the runoff pollution for different pollutants in each sub-catchment during the storm events, and the correlations between runoff pollution spatial variations and land-use patterns were tested by Spearman's rank correlation analysis. The results indicated that similar spatial variation trends were found for different pollutants (EPL or EMC) in light storm events, which strongly correlate with the proportion of residential land use; however, they have different trends in heavy storm events, which correlate with not only the residential land use, but also agricultural and bare land use. And some pairs of pollutants (such as COD/BOD, NH(3)-N/TN) might have the similar source because they have strong or moderate positive spatial correlation. Moreover, the first flush intensity (FF50) varies with impervious land areas and different interception ratio of initial storm runoff volume should be adopted in different sub-catchments. Copyright 2010 Elsevier B.V. All rights reserved.

  10. Spatially explicit modelling of cholera epidemics

    Science.gov (United States)

    Finger, F.; Bertuzzo, E.; Mari, L.; Knox, A. C.; Gatto, M.; Rinaldo, A.

    2013-12-01

    Epidemiological models can provide crucial understanding about the dynamics of infectious diseases. Possible applications range from real-time forecasting and allocation of health care resources to testing alternative intervention mechanisms such as vaccines, antibiotics or the improvement of sanitary conditions. We apply a spatially explicit model to the cholera epidemic that struck Haiti in October 2010 and is still ongoing. The dynamics of susceptibles as well as symptomatic and asymptomatic infectives are modelled at the scale of local human communities. Dissemination of Vibrio cholerae through hydrological transport and human mobility along the road network is explicitly taken into account, as well as the effect of rainfall as a driver of increasing disease incidence. The model is calibrated using a dataset of reported cholera cases. We further model the long term impact of several types of interventions on the disease dynamics by varying parameters appropriately. Key epidemiological mechanisms and parameters which affect the efficiency of treatments such as antibiotics are identified. Our results lead to conclusions about the influence of different intervention strategies on the overall epidemiological dynamics.

  11. Impact of spatial variation in snow water equivalent and snow ablation on spring snowcover depletion over an alpine ridge

    Science.gov (United States)

    Schirmer, Michael; Harder, Phillip; Pomeroy, John

    2016-04-01

    The spatial and temporal dynamics of mountain snowmelt are controlled by the spatial distribution of snow accumulation and redistribution and the pattern of melt energy applied to this snowcover. In order to better quantify the spatial variations of accumulation and ablation, Structure-from-Motion techniques were applied to sequential aerial photographs of an alpine ridge in the Canadian Rocky Mountains taken from an Unmanned Aerial Vehicle (UAV). Seven spatial maps of snow depth and changes to depth during late melt (May-July) were generated at very high resolutions covering an area of 800 x 600 m. The accuracy was assessed with over 100 GPS measurements and RMSE were found to be less than 10 cm. Low resolution manual measurements of density permitted calculation of snow water equivalent (SWE) and change in SWE (ablation rate). The results indicate a highly variable initial SWE distribution, which was five times more variable than the spatial variation in ablation rate. Spatial variation in ablation rate was still substantial, with a factor of two difference between north and south aspects and small scale variations due to local dust deposition. However, the impact of spatial variations in ablation rate on the snowcover depletion curve could not be discerned. The reason for this is that only a weak spatial correlation developed between SWE and ablation rate. These findings suggest that despite substantial variations in ablation rate, snowcover depletion curve calculations should emphasize the spatial variation of initial SWE rather than the variation in ablation rate. While there is scientific evidence from other field studies that support this, there are also studies that suggest that spatial variations in ablation rate can influence snowcover depletion curves in complex terrain, particularly in early melt. The development of UAV photogrammetry has provided an opportunity for further detailed measurement of ablation rates, SWE and snowcover depletion over complex

  12. Spatial variation in an avian host community: implications for disease dynamics.

    Science.gov (United States)

    States, Sarah L; Hochachka, Wesley M; Dhondt, André A

    2009-12-01

    Because many pathogens can infect multiple host species within a community, disease dynamics in a focal host species can be affected by the composition of the host community. We examine the extent to which spatial variation in species' abundances in an avian host community may contribute to geographically varying prevalence of a recently emerged wildlife pathogen. Mycoplasma gallisepticum is a pathogen novel to songbirds that has caused substantial mortality in house finches (Carpodacus mexicanus) in eastern North America. Though the house finch is the primary host species for M. gallisepticum, the American goldfinch (Spinus tristis) and northern cardinal (Cardinalis cardinalis) are alternate hosts, and laboratory experiments have demonstrated M. gallisepticum transmission between house finches and goldfinches. Still unknown is the real world impact on disease dynamics of variation in abundances of the three hosts. We analyzed data from winter-long bird and disease surveys in the northeastern United States. We found that higher disease prevalence in house finches was associated with higher numbers of northern cardinals and American goldfinches, although only the effect of cardinal abundance was statistically significant. Nevertheless, our results indicate that spatial variation in bird communities has the potential to cause geographic variation in disease prevalence in house finches.

  13. A space-time multiscale modelling of Earth's gravity field variations

    Science.gov (United States)

    Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric

    2017-04-01

    The mass distribution within the Earth varies over a wide range of spatial and temporal scales, generating variations in the Earth's gravity field in space and time. These variations are monitored by satellites as the GRACE mission, with a 400 km spatial resolution and 10 days to 1 month temporal resolution. They are expressed in the form of gravity field models, often with a fixed spatial or temporal resolution. The analysis of these models allows us to study the mass transfers within the Earth system. Here, we have developed space-time multi-scale models of the gravity field, in order to optimize the estimation of gravity signals resulting from local processes at different spatial and temporal scales, and to adapt the time resolution of the model to its spatial resolution according to the satellites sampling. For that, we first build a 4D wavelet family combining spatial Poisson wavelets with temporal Haar wavelets. Then, we set-up a regularized inversion of inter-satellites gravity potential differences in a bayesian framework, to estimate the model parameters. To build the prior, we develop a spectral analysis, localized in time and space, of geophysical models of mass transport and associated gravity variations. Finally, we test our approach to the reconstruction of space-time variations of the gravity field due to hydrology. We first consider a global distribution of observations along the orbit, from a simplified synthetic hydrology signal comprising only annual variations at large spatial scales. Then, we consider a regional distribution of observations in Africa, and a larger number of spatial and temporal scales. We test the influence of an imperfect prior and discuss our results.

  14. Evaluation of spatial and temporal variations in marine sediments quality using multivariate statistical techniques.

    Science.gov (United States)

    Alvarez, Odalys Quevedo; Tagle, Margarita Edelia Villanueva; Pascual, Jorge L Gómez; Marín, Ma Teresa Larrea; Clemente, Ana Catalina Nuñez; Medina, Miriam Odette Cora; Palau, Raiza Rey; Alfonso, Mario Simeón Pomares

    2014-10-01

    Spatial and temporal variations of sediment quality in Matanzas Bay (Cuba) were studied by determining a total of 12 variables (Zn, Cu, Pb, As, Ni, Co, Al, Fe, Mn, V, CO₃²⁻, and total hydrocarbons (THC). Surface sediments were collected, annually, at eight stations during 2005-2008. Multivariate statistical techniques, such as principal component (PCA), cluster (CA), and lineal discriminant (LDA) analyses were applied for identification of the most significant variables influencing the environmental quality of sediments. Heavy metals (Zn, Cu, Pb, V, and As) and THC were the most significant species contributing to sediment quality variations during the sampling period. Concentrations of V and As were determined in sediments of this ecosystem for the first time. The variation of sediment environmental quality with the sampling period and the differentiation of samples in three groups along the bay were obtained. The usefulness of the multivariate statistical techniques employed for the environmental interpretation of a limited dataset was confirmed.

  15. Spatial variations in isostatic compensation mechanisms of the Ninetyeast Ridge and their tectonic significance

    Science.gov (United States)

    Sreejith, K. M.; Krishna, K. S.

    2013-10-01

    Ninetyeast Ridge (NER), one of the longest linear volcanic features on the Earth, offers an excellent opportunity of understanding the isostatic response to the interactions of mantle plume with the migrating mid-ocean ridge. Bathymetry, geoid, and gravity (shipborne and satellite) data along 72 closely spaced transects and 17 overlapping grids on the NER are analyzed and modeled to determine the effective elastic thickness (Te) beneath the entire ridge. The results of 2-D and 3-D flexural modeling of the NER show large spatial variations in Te values ranging from 4 to 35 km, suggesting that the ridge was compensated along its length by different isostatic mechanisms. The southern (south of 22°S latitude) and northern (north of 2°N latitude) parts of the NER have Te values of >10 and >23 km, respectively, revealing that the southern part was emplaced on a lithosphere of intermediate strength possibly on flank of the Indian plate, whereas the northern part was emplaced in an intraplate setting. In contrast, in the central part of the NER (between latitudes 22°S and 2°N), highly variable Te values (4-22 km) are estimated. The scattered Te values in the central NER suggest that this part may have evolved due to the occurrence of frequent ridge jumps caused by the interaction of Kerguelen hot spot with rapid northward migration of the Wharton spreading ridge. Residual Mantle Bouguer Anomaly (RMBA) map of the NER and adjacent basins reveals that the entire length of the NER is associated with a significant negative anomaly up to 200 mGal, indicating the presence of thickened crust or less dense mantle beneath the ridge. 3-D crustal thickness map of the NER, generated by inversion of the RMBA data, shows a thick crust ranging from 15 to 19 km. The present study clearly shows that NER possesses a highly segmented isostatic pattern with the occurrence of subcrustal underplating or subsurface loading.

  16. Transient,spatially-varied recharge for groundwater modeling

    Science.gov (United States)

    Assefa, Kibreab; Woodbury, Allan

    2013-04-01

    This study is aimed at producing spatially and temporally varying groundwater recharge for transient groundwater modeling in a pilot watershed in the North Okanagan, Canada. The recharge modeling is undertaken by using a Richard's equation based finite element code (HYDRUS-1D) [Simunek et al., 2002], ArcGISTM [ESRI, 2011], ROSETTA [Schaap et al., 2001], in situ observations of soil temperature and soil moisture and a long term gridded climate data [Nielsen et al., 2010]. The public version of HYDUS-1D [Simunek et al., 2002] and another beta version with a detailed freezing and thawing module [Hansson et al., 2004] are first used to simulate soil temperature, snow pack and soil moisture over a one year experimental period. Statistical analysis of the results show both versions of HYDRUS-1D reproduce observed variables to the same degree. Correlation coefficients for soil temperature simulation were estimated at 0.9 and 0.8, at depths of 10 cm and 50 cm respectively; and for soil moisture, 0.8 and 0.6 at 10 cm and 50 cm respectively. This and other standard measures of model performance (root mean square error and average error) showed a promising performance of the HYDRUS-1D code in our pilot watershed. After evaluating model performance using field data and ROSETTA derived soil hydraulic parameters, the HYDRUS-1D code is coupled with ArcGISTM to produce spatially and temporally varying recharge maps throughout the Deep Creek watershed. Temporal and spatial analysis of 25 years daily recharge results at various representative points across the study watershed reveal significant temporal and spatial variations; average recharge estimated at 77.8 ± 50.8mm /year. This significant variation over the years, caused by antecedent soil moisture condition and climatic condition, illustrates the common flaw of assigning a constant percentage of precipitation throughout the simulation period. Groundwater recharge modeling has previously been attempted in the Okanagan Basin

  17. A flexible parametric approach to examining spatial variation in relative survival.

    Science.gov (United States)

    Cramb, Susanna M; Mengersen, Kerrie L; Lambert, Paul C; Ryan, Louise M; Baade, Peter D

    2016-12-20

    Most of the few published models used to obtain small-area estimates of relative survival are based on a generalized linear model with piecewise constant hazards under a Bayesian formulation. Limitations of these models include the need to artificially split the time scale, restricted ability to include continuous covariates, and limited predictive capacity. Here, an alternative Bayesian approach is proposed: a spatial flexible parametric relative survival model. This overcomes previous limitations by combining the benefits of flexible parametric models: the smooth, well-fitting baseline hazard functions and predictive ability, with the Bayesian benefits of robust and reliable small-area estimates. Both spatially structured and unstructured frailty components are included. Spatial smoothing is conducted using the intrinsic conditional autoregressive prior. The model was applied to breast, colorectal, and lung cancer data from the Queensland Cancer Registry across 478 geographical areas. Advantages of this approach include the ease of including more realistic complexity, the feasibility of using individual-level input data, and the capacity to conduct overall, cause-specific, and relative survival analysis within the same framework. Spatial flexible parametric survival models have great potential for exploring small-area survival inequalities, and we hope to stimulate further use of these models within wider contexts. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  18. Hierarchical Bayesian spatial models for multispecies conservation planning and monitoring.

    Science.gov (United States)

    Carroll, Carlos; Johnson, Devin S; Dunk, Jeffrey R; Zielinski, William J

    2010-12-01

    Biologists who develop and apply habitat models are often familiar with the statistical challenges posed by their data's spatial structure but are unsure of whether the use of complex spatial models will increase the utility of model results in planning. We compared the relative performance of nonspatial and hierarchical Bayesian spatial models for three vertebrate and invertebrate taxa of conservation concern (Church's sideband snails [Monadenia churchi], red tree voles [Arborimus longicaudus], and Pacific fishers [Martes pennanti pacifica]) that provide examples of a range of distributional extents and dispersal abilities. We used presence-absence data derived from regional monitoring programs to develop models with both landscape and site-level environmental covariates. We used Markov chain Monte Carlo algorithms and a conditional autoregressive or intrinsic conditional autoregressive model framework to fit spatial models. The fit of Bayesian spatial models was between 35 and 55% better than the fit of nonspatial analogue models. Bayesian spatial models outperformed analogous models developed with maximum entropy (Maxent) methods. Although the best spatial and nonspatial models included similar environmental variables, spatial models provided estimates of residual spatial effects that suggested how ecological processes might structure distribution patterns. Spatial models built from presence-absence data improved fit most for localized endemic species with ranges constrained by poorly known biogeographic factors and for widely distributed species suspected to be strongly affected by unmeasured environmental variables or population processes. By treating spatial effects as a variable of interest rather than a nuisance, hierarchical Bayesian spatial models, especially when they are based on a common broad-scale spatial lattice (here the national Forest Inventory and Analysis grid of 24 km(2) hexagons), can increase the relevance of habitat models to multispecies

  19. Spatial variations of methane emission in a large shallow eutrophic lake in subtropical climate

    Science.gov (United States)

    Xiao, Qitao; Zhang, Mi; Hu, Zhenghua; Gao, Yunqiu; Hu, Cheng; Liu, Cheng; Liu, Shoudong; Zhang, Zhen; Zhao, Jiayu; Xiao, Wei; Lee, X.

    2017-07-01

    Subtropical lakes are important source of atmospheric methane (CH4). This study aims to investigate spatial variations of CH4 flux in Lake Taihu, a large (area 2400 km2) and shallow (mean depth 1.9 m) eutrophic lake in Eastern China. The lake exhibited high spatial variations in pollution level, macrophyte vegetation abundance, and algal growth. We measured the diffusion CH4 flux via the transfer coefficient method across the whole lake. In addition, data obtained with the flux gradient and the eddy covariance methods were used in conjunction with the data on the diffusion flux to estimate the contribution by ebullition. Results from 3 years' measurements indicated high spatial variabilities in the diffusion CH4 flux. The spatial pattern of the diffusion CH4 emission was correlated with water clarity, dissolved oxygen concentration, and the spatial distributions of algal and submerged vegetation. In comparison to the transfer coefficient method, the eddy covariance and the flux gradient method observed a lake CH4 flux that was 3.39 ± 0.58 (mean ± 1 standard deviation) and 1.95 ± 0.36 times higher in an open-water eutrophic zone and in a habitat of submerged macrophytes, respectively. The result implied an average of 71% and 49% ebullition contribution to the total CH4 flux in the two zones. The annual mean diffusion CH4 flux of the whole lake was 0.54 ± 0.30 g m-2 yr-1. Our CH4 emission data suggest that the average CH4 emission reported previously for lakes in Eastern China was overestimated.

  20. The impacts of disturbance on the spatial and temporal variations of carbon balance in forest ecosystems on Hokkaido, Japan

    Science.gov (United States)

    Hirata, R.; Ito, A.; Saigusa, N.

    2013-12-01

    Carbon balance in a forest ecosystem can be quite variable if the forest ecosystem structure and function change abruptly as a result of disturbance and subsequent recovery processes. A map of forest age is useful for upscaling carbon balance from the site level to a regional scale because it provides information about when disturbance occurred and how it spread over a wide area. In this study, we used maps of forest age to help evaluate spatial and temporal variations in the carbon balance of forest ecosystems with a process-based ecosystem model. Forests less than 60 years old account for more than 70% of Japanese forests because forest stands have been quickly replaced after disturbance caused by thinning, harvesting, plantations, fires, typhoons, and insect damage. However, few studies have attempted to quantify how much disturbance affects the spatial and temporal variations of carbon balance. In this study, we focused on how disturbance and subsequent re-growth affected the spatial and temporal variations of the carbon balance of forests. We adapted the Vegetation Integrative SImulator for Trace Gases (VISIT) model in order to simulate carbon balance on Hokkaido, which is the northernmost island of Japan. The model was validated with tower flux data obtained from forests with ages between 0 and 43 years. Simulations of the carbon balance were conducted for the period 1948-2010 after a 1000-year spin-up at a spatial resolution of 1 km × 1 km. We investigated two case studies of simulated carbon balance: one that took into account the spatial distribution of forest ages derived from forest inventory data, and another that ignored the impact of disturbance (i.e., no disturbance and a homogeneous distribution of ages). We first focused on the difference from 2000-2010 in the spatial distribution of net ecosystem production (NEP) between the disturbance and non-disturbance cases. In the non-disturbance case, the temporal and spatial changes in NEP were gradual

  1. A Model of Colonic Crypts using SBML Spatial

    Directory of Open Access Journals (Sweden)

    Carlo Maj

    2013-09-01

    Full Text Available The Spatial Processes package enables an explicit definition of a spatial environment on top of the normal dynamic modeling SBML capabilities. The possibility of an explicit representation of spatial dynamics increases the representation power of SBML. In this work we used those new SBML features to define an extensive model of colonic crypts composed of the main cellular types (from stem cells to fully differentiated cells, alongside their spatial dynamics.

  2. Spatial Variations of Soil Microbial Activities in Saline Groundwater-Irrigated Soil Ecosystem.

    Science.gov (United States)

    Chen, Li-Juan; Feng, Qi; Li, Chang-Sheng; Song, You-Xi; Liu, Wei; Si, Jian-Hua; Zhang, Bao-Gui

    2016-05-01

    Spatial variations of soil microbial activities and its relationship with environmental factors are very important for estimating regional soil ecosystem function. Based on field samplings in a typical saline groundwater-irrigated region, spatial variations of soil microbial metabolic activities were investigated. Combined with groundwater quality analysis, the relationship between microbial activities and water salinity was also studied. The results demonstrated that moderate spatial heterogeneity of soil microbial activities presented under the total dissolved solids (TDS) of groundwater ranging from 0.23 to 12.24 g L(-1). Groundwater salinity and microbial activities had almost opposite distribution characteristics: slight saline water was mainly distributed in west Baqu and south Quanshan, while severe saline and briny water were dominant in east Baqu and west Huqu; however, total AWCD was higher in the east-center and southwest of Baqu and east Huqu, while it was lower in east Baqu and northwest Huqu. The results of correlation analyses demonstrated that high-salinity groundwater irrigation had significantly adverse effects on soil microbial activities. Major ions Ca(2+), Mg(2+), Cl(-), and SO4(2-) in groundwater decisively influenced the results. Three carbon sources, carbohydrates, amines, and phenols, which had minor utilization rates in all irrigation districts, were extremely significantly affected by high-salinity groundwater irrigation. The results presented here offer an approach for diagnosing regional soil ecosystem function changes under saline water irrigation.

  3. Spatial variation of peat soil properties in the oil-producing region of northeastern Sakhalin

    Science.gov (United States)

    Lipatov, D. N.; Shcheglov, A. I.; Manakhov, D. V.; Zavgorodnyaya, Yu. A.; Rozanova, M. S.; Brekhov, P. T.

    2017-07-01

    Morphology and properties of medium-deep oligotrophic peat, oligotrophic peat gley, pyrogenic oligotrophic peat gley, and peat gley soils on subshrub-cotton grass-sphagnum bogs and in swampy larch forests of northeastern Sakhalin have been studied. Variation in the thickness and reserves of litters in the studied bog and forest biogeocenoses has been analyzed. The profile distribution and spatial variability of moisture, density, ash, and pHKCl in separate groups of peat soils have been described. The content and spatial variability of petroleum hydrocarbons have been considered in relation to the accumulation of natural bitumoids by peat soils and the technogenic pressing in the oil-producing region. Variation of each parameter at different distances (10, 50, and 1000 m) has been estimated using a hierarchical sampling scheme. The spatial conjugation of soil parameters has been studied by factor analysis using the principal components method and Spearman correlation coefficients. Regression equations have been proposed to describe relationships of ash content with soil density and content of petroleum hydrocarbons in peat horizons.

  4. Spatial Data Web Services Pricing Model Infrastructure

    Science.gov (United States)

    Ozmus, L.; Erkek, B.; Colak, S.; Cankurt, I.; Bakıcı, S.

    2013-08-01

    most important law with related NSDI is the establishment of General Directorate of Geographic Information System under the Ministry of Environment and Urbanism. due to; to do or to have do works and activities with related to the establishment of National Geographic Information Systems (NGIS), usage of NGIS and improvements of NGIS. Outputs of these projects are served to not only public administration but also to Turkish society. Today for example, TAKBIS data (cadastre services) are shared more than 50 institutions by Web services, Tusaga-Aktif system has more than 3800 users who are having real-time GPS data correction, Orthophoto WMS services has been started for two years as a charge of free. Today there is great discussion about data pricing among the institutions. Some of them think that the pricing is storage of the data. Some of them think that the pricing is value of data itself. There is no certain rule about pricing. On this paper firstly, pricing of data storage and later on spatial data pricing models in different countries are investigated to improve institutional understanding in Turkey.

  5. Spatial and temporal variation of stable isotopes in precipitation across Costa Rica

    Science.gov (United States)

    Welsh Unwala, K.; Sanchez-Murillo, R.; Esquivel-Hernandez, G.; Brooks, E. S.; Boll, J.; Alfaro-Solis, R.; Valdes-Gonzalez, J.

    2013-12-01

    The geographic location of Costa Rica on the Central American Isthmus creates unique mountainous microclimate systems across the country that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. These microclimate systems offer an exceptional opportunity to study isotopic variations in precipitation over the Central American continental divide. Here, we present a spatial and temporal analysis of historic Global Network of Isotopes in Precipitation (GNIP) records and current monitoring efforts. GNIP Sampling campaigns were mainly comprised of monthly-integrated samples during intermittent years from 1990 to 2005. Ongoing monitoring includes three distinct microclimate locations along the continental divide. Samples were grouped into four main regions: Nicoya Peninsula (δ2H = 6.65δ18O-0.13; r2=0.86); Pacific Coast (δ2H = 7.60δ18O+7.95; r2=0.99); Caribbean Slope (δ2H = 6.97δ18O+4.97; r2=0.97); and Central Valley (δ2H = 7.94δ18O+10.38; r2=0.98). The overall meteoric water line for Costa Rica can be defined as δ2H = 7.61δ18O+7.40 (r2=0.98). The regression of precipitation amount with annual arithmetic means in samples from all four regions yields a slope of -1.6 ‰ δ18O per 100 mm of rain (r2 = 0.57), which corresponds with a temperature effect of -0.37 ‰ δ18O/°C. A strong correlation (r2=0.77) of -2.0 ‰ δ18O per km of elevation was found. Samples within the Nicoya Peninsula and Caribbean lowlands appear to be dominated by evaporation enrichment, especially during the dry months (January-April), likely resulting from small precipitation amounts. In the inter-mountainous region of the Central Valley and Pacific slope, complex moisture recycling processes may dominate isotopic variations. Generally, isotopic values tend to be more depleted as the rainy season progresses over the year (May-October). HYSPLIT back trajectory analyses indicate that enriched isotopic compositions are related to central Caribbean parental moisture

  6. Spatial variations in estimated chronic exposure to traffic-related air pollution in working populations: A simulation

    Directory of Open Access Journals (Sweden)

    Cloutier-Fisher Denise

    2008-07-01

    Full Text Available Abstract Background Chronic exposure to traffic-related air pollution is associated with a variety of health impacts in adults and recent studies show that exposure varies spatially, with some residents in a community more exposed than others. A spatial exposure simulation model (SESM which incorporates six microenvironments (home indoor, work indoor, other indoor, outdoor, in-vehicle to work and in-vehicle other is described and used to explore spatial variability in estimates of exposure to traffic-related nitrogen dioxide (not including indoor sources for working people. The study models spatial variability in estimated exposure aggregated at the census tracts level for 382 census tracts in the Greater Vancouver Regional District of British Columbia, Canada. Summary statistics relating to the distributions of the estimated exposures are compared visually through mapping. Observed variations are explored through analyses of model inputs. Results Two sources of spatial variability in exposure to traffic-related nitrogen dioxide were identified. Median estimates of total exposure ranged from 8 μg/m3 to 35 μg/m3 of annual average hourly NO2 for workers in different census tracts in the study area. Exposure estimates are highest where ambient pollution levels are highest. This reflects the regional gradient of pollution in the study area and the relatively high percentage of time spent at home locations. However, for workers within the same census tract, variations were observed in the partial exposure estimates associated with time spent outside the residential census tract. Simulation modeling shows that some workers may have exposures 1.3 times higher than other workers residing in the same census tract because of time spent away from the residential census tract, and that time spent in work census tracts contributes most to the differences in exposure. Exposure estimates associated with the activity of commuting by vehicle to work were

  7. Spatial variation of the etch rate for deep etching of silicon by reactive ion etching

    DEFF Research Database (Denmark)

    Andersen, Bo Asp Møller; Hansen, Ole; Kristensen, Martin

    1997-01-01

    The macroscopic uniformity of deep etching into silicon by reactive ion etching (RIE) with a SF6-O-2 plasma was studied. The spatial variation of the etch rate across a 4 inch wafer in a single wafer system is a function of the process parameters and the configuration of the etch chamber. It was ......The macroscopic uniformity of deep etching into silicon by reactive ion etching (RIE) with a SF6-O-2 plasma was studied. The spatial variation of the etch rate across a 4 inch wafer in a single wafer system is a function of the process parameters and the configuration of the etch chamber....... It was found that, for a constant load of silicon exposed to the plasma, the etch rate variation can be controlled through the applied rf power, the chamber pressure, and the gas mixture. It was also found that the etch rate uniformity varies with the load of silicon exposed to the plasma. The result...... is a balance between the flux of neutral radicals and the flux of energetic ions to the surface. This balance is due to the RIE etch mechanism, which involves synergism between the two fluxes. (C) 1997 American Vacuum Society....

  8. Spatial and seasonal variations in bacterial communities of the Yellow Sea by T-RFLP analysis

    Institute of Scientific and Technical Information of China (English)

    Hongyuan WANG; Xiaolu JIANG; Ya HE; Huashi GUAN

    2009-01-01

    Four typical coastal sites (rocky shore, sandy shore, mud flat shore, and artificial harbor) at the Yellow Sea were chosen to investigate the spatial and seasonal variations in bacterial communities. This was accomplished by using terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR amplified 16S rDNA fragments. Two kinds of tetrameric restriction enzymes, HhaI and MspI, were used in the experiment to depict the bacterial community diversity in different marine environments. It was found that the community compositions digested by the two enzymes separately were different. However, the results of bacterial community diversity derived from them were similar. The MDA analysis results of T-RFLP profiles coming from HhaI and MspI both exhibited a significant seasonal community shift for bacteria and a relatively low spatial variation among the four locations. With HhaI as the sample, the pair wise T-tests also revealed that variations were minor between each pair of marine environments, with R ranging from 0.198 to 0.349. However, the bacterial community structure in the mud flat site depicted a larger difference than each of the other three sites (R ranging from 0.282 to 0.349).

  9. Spatial variation in river runoff into a coastal area — An ecological approach

    Science.gov (United States)

    Vinagre, C.; Máguas, C.; Cabral, H. N.; Costa, M. J.

    2011-04-01

    Carbon and nitrogen stable isotopes were used to investigate spatial variation in terrestrial particulate organic matter (POM) input to a coastal area off the Tagus river estuary. Isotopic variation in higher trophic level organisms was also examined, along the coast. This study was carried out in late summer, after a period of 3 months of low river flow. The overall aim was to determine if under such conditions the coastal area is enriched by the river plume and, particularly, if lower secondary productivity should be expected in some areas. Spatial variation was detected as a gradient of decreasing terrestrial input with increasing distance from the river. It was concluded that terrestrial carbon input was also incorporated into higher trophic levels and that organisms with lower mobility are more sensitive to the gradient in terrestrial input. Even in low flow conditions the whole fishing area remained under the influence of the river plume, which still accounted for 24% of the total POM 30 km from the river mouth. Additionally, δ 15N values indicated pollution input from the river Tagus.

  10. Spatial air pollution modelling for a West-African town

    Directory of Open Access Journals (Sweden)

    Sirak Zenebe Gebreab

    2015-11-01

    Full Text Available Land use regression (LUR modelling is a common approach used in European and Northern American epidemiological studies to assess urban and traffic related air pollution exposures. Studies applying LUR in Africa are lacking. A need exists to understand if this approach holds for an African setting, where urban features, pollutant exposures and data availability differ considerably from other continents. We developed a parsimonious regression model based on 48-hour nitrogen dioxide (NO2 concentrations measured at 40 sites in Kaédi, a medium sized West-African town, and variables generated in a geographic information system (GIS. Road variables and settlement land use characteristics were found to be important predictors of 48-hour NO2 concentration in the model. About 68% of concentration variability in the town was explained by the model. The model was internally validated by leave-one-out cross-validation and it was found to perform moderately well. Furthermore, its parameters were robust to sampling variation. We applied the model at 100 m pixels to create a map describing the broad spatial pattern of NO2 across Kaédi. In this research, we demonstrated the potential for LUR as a valid, cost-effective approach for air pollution modelling and mapping in an African town. If the methodology were to be adopted by environmental and public health authorities in these regions, it could provide a quick assessment of the local air pollution burden and potentially support air pollution policies and guidelines.

  11. Spatial variations in immediate greenhouse gases and aerosol emissions and resulting radiative forcing from wildfires in interior Alaska

    Science.gov (United States)

    Huang, Shengli; Liu, Heping; Dahal, Devendra; Jin, Suming; Li, Shuang; Liu, Shu-Guang

    2016-01-01

    Boreal fires can cool the climate; however, this conclusion came from individual fires and may not represent the whole story. We hypothesize that the climatic impact of boreal fires depends on local landscape heterogeneity such as burn severity, prefire vegetation type, and soil properties. To test this hypothesis, spatially explicit emission of greenhouse gases (GHGs) and aerosols and their resulting radiative forcing are required as an important and necessary component towards a full assessment. In this study, we integrated remote sensing (Landsat and MODIS) and models (carbon consumption model, emission factors model, and radiative forcing model) to calculate the carbon consumption, GHGs and aerosol emissions, and their radiative forcing of 2001–2010 fires at 30 m resolution in the Yukon River Basin of Alaska. Total carbon consumption showed significant spatial variation, with a mean of 2,615 g C m−2 and a standard deviation of 2,589 g C m−2. The carbon consumption led to different amounts of GHGs and aerosol emissions, ranging from 593.26 Tg (CO2) to 0.16 Tg (N2O). When converted to equivalent CO2 based on global warming potential metric, the maximum 20 years equivalent CO2 was black carbon (713.77 Tg), and the lowest 20 years equivalent CO2 was organic carbon (−583.13 Tg). The resulting radiative forcing also showed significant spatial variation: CO2, CH4, and N2O can cause a 20-year mean radiative forcing of 7.41 W m−2 with a standard deviation of 2.87 W m−2. This emission forcing heterogeneity indicates that different boreal fires have different climatic impacts. When considering the spatial variation of other forcings, such as surface shortwave forcing, we may conclude that some boreal fires, especially boreal deciduous fires, can warm the climate.

  12. Spatial Variations of Soil Gas Geochemistry in the Tangshan Area of Northern China

    Directory of Open Access Journals (Sweden)

    Ying Li

    2013-01-01

    Full Text Available The concentrations of Hg, Rn, H2, He and CO2 in soil gases at 756 sites were measured in the Tangshan area where Ms 7.8 earthquake occurred in 1976 and is characterized by complex tectonic structures and high seismic hazard. The results showed that, spatial variations of the gaseous anomalies, especially hydrogen and helium have spatial congruence along the tectonic lines, which can be attributed to their deep sources and the migration paths formed by the faults. A better congruence of radon and carbon dioxide is highlighted which indicates that carbon dioxide acts as the carrier gas for radon in this area. Two geochemical anomaly zones of soil gas were found in the area wherein all the studied gases exhibited anomalies or high values, related to the faults and earthquakes.

  13. Spatial Variations of Soil Gas Geochemistry in the Tangshan Area of Northern China

    Directory of Open Access Journals (Sweden)

    Ying Li

    2013-01-01

    Full Text Available The concentrations of Hg, Rn, H2, He and CO2 in soil gases at 756 sites were measured in the Tangshan area where Ms 7.8 earthquake occurred in 1976 and is characterized by complex tectonic structures and high seismic hazard. The results showed that, spatial variations of the gaseous anomalies, especially hydrogen and helium have spatial congruence along the tectonic lines, which can be attributed to their deep sources and the migration paths formed by the faults. A better congruence of radon and carbon dioxide is highlighted which indicates that carbon dioxide acts as the carrier gas for radon in this area. Two geochemical anomaly zones of soil gas were found in the area wherein all the studied gases exhibited anomalies or high values, related to the faults and earthquakes.

  14. Spatial and temporal variation in dissolved organic carbon composition in a peaty catchment draining a windfarm

    Science.gov (United States)

    Zheng, Ying; Waldron, Susan; Flowers, Hugh

    2015-04-01

    Peatlands are an important terrestrial carbon reserve and a principal source of dissolved organic carbon (DOC) to the fluvial environment (Wallage et al. 2006). Recently it has been observed that DOC concentrations [DOC] in surface waters have increased in Europe and North America (Monteith et al. 2007). This has been attributed primarily to reduced acid deposition. However, land use change can also release C from peat soils. A significant land use change in Scotland is hosting windfarms. Whether windfarm construction causes such impacts has been a research focus, particularly considering fluvial losses, but usually assessing if there are changes in DOC concentration rather than composition. Our study area is a peaty catchment that hosts wind turbines, has peat restoration activities and forest felling and is drained by two streams. We are using UV-visible and fluorescence spectrophotometry to assess if there are differences between the two steams or temporal changes in DOC composition. We will present data from samples collected since February 2014. The parameters we are focusing on are SUVA254, E4/E6 and E2/E4 ratios as these are indicators of DOC aromaticity, humic acid (HA): fulvic acid (FA) ratio and the proportion of humic substances in DOC (Weishaar, 2003; Spencer et al. 2007; Graham et al. 2012). To assess these we have measured UV-visible absorbance spectra from 200 nm to 800 nm. Meanwhile sample fluorescence emission and excitation matrix (EEM) will be applied with the PARAFAC model to obtain more information about the variations in humic substances in this catchment. Our current analysis indicates spatial differences not only in DOC concentration but also in composition. For example, the mainstem draining the windfarm area had a smaller [DOC] but higher E4/E6 and lower E2/E4 ratio values than the tributary draining an area of felled forestry. This may be indicative of more HAs in the mainstem DOC. Seasonal variations have also been observed. Both streams

  15. Estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using Scots pine inventories

    Directory of Open Access Journals (Sweden)

    P. Ala-aho

    2014-07-01

    Full Text Available Climate change and land use are rapidly changing the amount and temporal distribution of recharge in northern aquifers. This paper presents a novel method for distributing Monte Carlo simulations of 1-D soil profile spatially to estimate transient recharge in an unconfined esker aquifer. The modeling approach uses data-based estimates for the most important parameters controlling the total amount (canopy cover and timing (depth of the unsaturated zone of groundwater recharge. Scots pine canopy was parameterized to leaf area index (LAI using forestry inventory data. Uncertainty in the parameters controlling soil hydraulic properties and evapotranspiration was carried over from the Monte Carlo runs to the final recharge estimates. Different mechanisms for lake, soil, and snow evaporation and transpiration were used in the model set-up. Finally, the model output was validated with independent recharge estimates using the water table fluctuation method and baseflow estimation. The results indicated that LAI is important in controlling total recharge amount, and the modeling approach successfully reduced model uncertainty by allocating the LAI parameter spatially in the model. Soil evaporation compensated for transpiration for areas with low LAI values, which may be significant in optimal management of forestry and recharge. Different forest management scenarios tested with the model showed differences in annual recharge of up to 100 mm. The uncertainty in recharge estimates arising from the simulation parameters was lower than the interannual variation caused by climate conditions. It proved important to take unsaturated depth and vegetation cover into account when estimating spatially and temporally distributed recharge in sandy unconfined aquifers.

  16. Mathematical Modeling of spatial disease variables by Spatial Fuzzy Logic for Spatial Decision Support Systems

    Science.gov (United States)

    Platz, M.; Rapp, J.; Groessler, M.; Niehaus, E.; Babu, A.; Soman, B.

    2014-11-01

    A Spatial Decision Support System (SDSS) provides support for decision makers and should not be viewed as replacing human intelligence with machines. Therefore it is reasonable that decision makers are able to use a feature to analyze the provided spatial decision support in detail to crosscheck the digital support of the SDSS with their own expertise. Spatial decision support is based on risk and resource maps in a Geographic Information System (GIS) with relevant layers e.g. environmental, health and socio-economic data. Spatial fuzzy logic allows the representation of spatial properties with a value of truth in the range between 0 and 1. Decision makers can refer to the visualization of the spatial truth of single risk variables of a disease. Spatial fuzzy logic rules that support the allocation of limited resources according to risk can be evaluated with measure theory on topological spaces, which allows to visualize the applicability of this rules as well in a map. Our paper is based on the concept of a spatial fuzzy logic on topological spaces that contributes to the development of an adaptive Early Warning And Response System (EWARS) providing decision support for the current or future spatial distribution of a disease. It supports the decision maker in testing interventions based on available resources and apply risk mitigation strategies and provide guidance tailored to the geo-location of the user via mobile devices. The software component of the system would be based on open source software and the software developed during this project will also be in the open source domain, so that an open community can build on the results and tailor further work to regional or international requirements and constraints. A freely available EWARS Spatial Fuzzy Logic Demo was developed wich enables a user to visualize risk and resource maps based on individual data in several data formats.

  17. Utilizing spatial demographic and life history variation to optimize sustainable yield of a temperate sex-changing fish.

    Directory of Open Access Journals (Sweden)

    Scott L Hamilton

    Full Text Available Fish populations vary geographically in demography and life history due to environmental and ecological processes and in response to exploitation. However, population dynamic models and stock assessments, used to manage fisheries, rarely explicitly incorporate spatial variation to inform management decisions. Here, we describe extensive geographic variation in several demographic and life history characteristics (e.g., size structure, growth, survivorship, maturation, and sex change of California sheephead (Semicossyphus pulcher, a temperate rocky reef fish targeted by recreational and commercial fisheries. Fish were sampled from nine locations throughout southern California in 2007-2008. We developed a dynamic size and age-structured model, parameterized separately for each location, to assess the potential cost or benefit in terms of fisheries yield and conservation objectives of changing minimum size limits and/or fishing mortality rates (compared to the status quo. Results indicate that managing populations individually, with location-specific regulations, could increase yield by over 26% while maintaining conservative levels of spawning biomass. While this local management approach would be challenging to implement in practice, we found statistically similar increases in yield could be achieved by dividing southern California into two separate management regions, reflecting geographic similarities in demography. To maximize yield, size limits should be increased by 90 mm in the northern region and held at current levels in the south. We also found that managing the fishery as one single stock (the status quo, but with a size limit 50 mm greater than the current regulations, could increase overall fishery yield by 15%. Increases in size limits are predicted to enhance fishery yield and may also have important ecological consequences for the predatory role of sheephead in kelp forests. This framework for incorporating demographic variation

  18. Testing spatial α-variation with optical atomic clocks based on highly charged ions

    Directory of Open Access Journals (Sweden)

    Berengut J. C.

    2013-08-01

    Full Text Available We review recent works illustrating the potential use of highly charged ions as the basis of optical atomic clocks of exceptional accuracy and very high sensitivity to variation of the fine structure constant, α. The tendency towards large transition energies in highly charged ions can be overcome using level crossings, which allow transitions between different orbitals to be within the range of usual lasers. We present simple scaling laws that demonstrate reduced systematics that could be realised in highly charged ion clocks. Such clocks could allow us to corroborate astronomical studies that suggest a spatial gradient in values of α across the Universe.

  19. Spatial and seasonal variations of the contamination within water body of the Grand Canal, China.

    Science.gov (United States)

    Xiaolong, Wang; Jingyi, Han; Ligang, Xu; Qi, Zhang

    2010-05-01

    To delineate the character of contaminations in the Grand Canal, China, a three-year study (2004-2006) was conducted to investigate variations the water quality in the canal. Results showed that the variation of water quality within the Grand Canal was of there is remarkable spatial and seasonal heterogeneity regarding water quality within the Canal. Values of contaminants in dry-season were obviously higher than those in wet-season. Sites influenced strongly by industry and urbanization showed higher contents of nutrients and lower levels of dissolved oxygen in water body; moreover these sites were severely polluted by dissolved metals with the contents of cadmium, chromium and copper exceeding the Criteria Maximum Concentration (CMC), US EPA. Multivariate statistical analysis suggested nutrient and dissolved metals pollution was the dominant environmental problems within the Canal. Anthropogenic influences played a dominant role in the character of contaminations in the Grand Canal. Copyright 2010 Elsevier Ltd. All rights reserved.

  20. Indication of spatial variations in annual cycles of functional groups of planktonic ciliates to environmental change in marine ecosystems.

    Science.gov (United States)

    Xu, Henglong; Jiang, Yong; Xu, Guangjian; Warren, Alan

    2017-03-15

    The indication of spatial variations in annual cycles of functional groups of planktonic ciliates to environmental changes was studied in a bay, northern Yellow Sea. Samples were biweekly collected at five stations with different hydrographic conditions during a 1-year cycle. The second-stage-matrix-based multivariate approach was used to summarize the internal interactions of the ciliate functional groups among five stations during a 1-year period. The functional groups of the ciliates represented a clear spatial variation in annual cycle among five stations. Mantel analysis demonstrated that the spatial variation in annual cycles of the ciliate functional groups were significantly correlated with the changes nutrients (mainly soluble reactive phosphates and nitrates), alone or in combination with salinity among five stations. Based the results, it is suggested that the spatial variation in annual cycles of functional groups of planktonic ciliates may indicated the changes of hydrographic conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Spatial Econometric data analysis: moving beyond traditional models

    NARCIS (Netherlands)

    Florax, R.J.G.M.; Vlist, van der A.J.

    2003-01-01

    This article appraises recent advances in the spatial econometric literature. It serves as the introduction too collection of new papers on spatial econometric data analysis brought together in this special issue, dealing specifically with new extensions to the spatial econometric modeling perspecti

  2. Strong limit on the spatial and temporal variations of the fine-structure constant

    Science.gov (United States)

    Le, T. D.

    2016-10-01

    Observed spectra of quasars provide a powerful tool to test the possible spatial and temporal variations of the fine-structure constant α = e 2/ћc over the history of the Universe. It is demonstrated that high sensitivity to the variation of α can be obtained from a comparison of the spectra of quasars and laboratories. We reported a new constraint on the variation of the fine-structure constant based on the analysis of the optical spectra of the fine-structure transitions in [NeIII], [NeV], [OIII], [OI] and [SII] multiplets from 14 Seyfert 1.5 galaxies. The weighted mean value of the α-variation derived from our analysis over the redshift range 0.035 < z < 0.281 Δα/α= (4.50 +/- 5.53) \\times 10-5. This result presents strong limit improvements on the constraint on Δα/α compared to the published in the literature

  3. The variation of the fine structure constant: testing the dipole model with thermonuclear supernovae

    CERN Document Server

    Kraiselburd, Lucila; Negrelli, Carolina; Berro, Enrique García

    2014-01-01

    The large-number hypothesis conjectures that fundamental constants may vary. Accordingly, the spacetime variation of fundamental constants has been an active subject of research for decades. Recently, using data obtained with large telescopes a phenomenological model in which the fine structure constant might vary spatially has been proposed. We test whether this hypothetical spatial variation of {\\alpha}, which follows a dipole law, is compatible with the data of distant thermonuclear supernovae. Unlike previous works, in our calculations we consider not only the variation of the luminosity distance when a varying {\\alpha} is adopted, but we also take into account the variation of the peak luminosity of Type Ia supernovae resulting from a variation of {\\alpha}. This is done using an empirical relation for the peak bolometric magnitude of thermonuclear supernovae that correctly reproduces the results of detailed numerical simulations. We find that there is no significant difference between the several phenome...

  4. Spatially explicit fate modelling of nanomaterials in natural waters

    NARCIS (Netherlands)

    Quik, J.T.K.; Klein, de J.J.M.; Koelmans, A.A.

    2015-01-01

    Site specific exposure assessments for engineered nanoparticles (ENPs) require spatially explicit fate models, which however are not yet available. Here we present an ENP fate model (NanoDUFLOW) that links ENP specific process descriptions to a spatially explicit hydrological model. The link enables

  5. Mining multilevel spatial association rules with cloud models

    Institute of Scientific and Technical Information of China (English)

    YANG Bin; ZHU Zhong-ying

    2005-01-01

    The traditional generalization-based knowledge discovery method is introduced. A new kind of multilevel spatial association of the rules mining method based on the cloud model is presented. The cloud model integrates the vague and random use of linguistic terms in a unified way. With these models, spatial and nonspatial attribute values are well generalized at multiple levels, allowing discovery of strong spatial association rules.Combining the cloud model based method with Apriori algorithms for mining association rules from a spatial database shows benefits in being effective and flexible.

  6. Sensitivity of grassland plant community composition to spatial vs. temporal variation in precipitation.

    Science.gov (United States)

    Cleland, Elsa E; Collins, Scott L; Dickson, Timothy L; Farrer, Emily C; Gross, Katherine L; Gherardi, Laureano A; Hallett, Lauren M; Hobbs, Richard J; Hsu, Joanna S; Turnbull, Laura; Suding, Katharine N

    2013-08-01

    Climate gradients shape spatial variation in the richness and composition of plant communities. Given future predicted changes in climate means and variability, and likely regional variation in the magnitudes of these changes, it is important to determine how temporal variation in climate influences temporal variation in plant community structure. Here, we evaluated how species richness, turnover, and composition of grassland plant communities responded to interannual variation in precipitation by synthesizing long-term data from grasslands across the United States. We found that mean annual precipitation,(MAP) was a positive predictor of species richness across sites, but a positive temporal relationship between annual precipitation and richness was only evident within two sites with low MAP. We also found higher average rates of species turnover in dry sites that in turn had a high proportion of annual species, although interannual rates of species turnover were surprisingly high across all locations. Annual species were less abundant than perennial species at nearly all sites, and our analysis showed that the probability of a species being lost or gained from one year to the next increased with decreasing species abundance. Bray-Curtis dissimilarity from one year to the next, a measure of species composition change that is influenced mainly by abundant species, was insensitive to precipitation at all sites. These results suggest that the richness and turnover patterns we observed were driven primarily by rare species, which comprise the majority of the local species pools at these grassland sites. These findings are consistent with the idea that short-lived and less abundant species are more sensitive to interannual climate variability than longer-lived and more abundant species. We conclude that, among grassland ecosystems, xeric grasslands are likely to exhibit the greatest responsiveness of community composition (richness and turnover) to predicted future

  7. [Prediction of spatial distribution of forest carbon storage in Heilongjiang Province using spatial error model].

    Science.gov (United States)

    Liu, Chang; Li, Feng-Ri; Zhen, Zhen

    2014-10-01

    Abstract: Based on the data from Chinese National Forest Inventory (CNFI) and Key Ecological Benefit Forest Monitoring plots (5075 in total) in Heilongjiang Province in 2010 and concurrent meteorological data coming from 59 meteorological stations located in Heilongjiang, Jilin and Inner Mongolia, this paper established a spatial error model (SEM) by GeoDA using carbon storage as dependent variable and several independent variables, including diameter of living trees (DBH), number of trees per hectare (TPH), elevation (Elev), slope (Slope), and product of precipitation and temperature (Rain_Temp). Global Moran's I was computed for describing overall spatial autocorrelations of model results at different spatial scales. Local Moran's I was calculated at the optimal bandwidth (25 km) to present spatial distribution residuals. Intra-block spatial variances were computed to explain spatial heterogeneity of residuals. Finally, a spatial distribution map of carbon storage in Heilongjiang was visualized based on predictions. The results showed that the distribution of forest carbon storage in Heilongjiang had spatial effect and was significantly influenced by stand, topographic and meteorological factors, especially average DBH. SEM could solve the spatial autocorrelation and heterogeneity well. There were significant spatial differences in distribution of forest carbon storage. The carbon storage was mainly distributed in Zhangguangcai Mountain, Xiao Xing'an Mountain and Da Xing'an Mountain where dense, forests existed, rarely distributed in Songnen Plains, while Wanda Mountain had moderate-level carbon storage.

  8. Temporal and spatial distribution characteristics of water resources in Guangdong Province based on a cloud model

    Directory of Open Access Journals (Sweden)

    Qi Zhou

    2015-10-01

    Full Text Available With a focus on the difficulty of quantitatively describing the degree of nonuniformity of temporal and spatial distributions of water resources, quantitative research was carried out on the temporal and spatial distribution characteristics of water resources in Guangdong Province from 1956 to 2000 based on a cloud model. The spatial variation of the temporal distribution characteristics and the temporal variation of the spatial distribution characteristics were both analyzed. In addition, the relationships between the numerical characteristics of the cloud model of temporal and spatial distributions of water resources and precipitation were also studied. The results show that, using a cloud model, it is possible to intuitively describe the temporal and spatial distribution characteristics of water resources in cloud images. Water resources in Guangdong Province and their temporal and spatial distribution characteristics are differentiated by their geographic locations. Downstream and coastal areas have a larger amount of water resources with greater uniformity and stronger stability in terms of temporal distribution. Regions with more precipitation possess larger amounts of water resources, and years with more precipitation show greater nonuniformity in the spatial distribution of water resources. The correlation between the nonuniformity of the temporal distribution and local precipitation is small, and no correlation is found between the stability of the nonuniformity of the temporal and spatial distributions of water resources and precipitation. The amount of water resources in Guangdong Province shows an increasing trend from 1956 to 2000, the nonuniformity of the spatial distribution of water resources declines, and the stability of the nonuniformity of the spatial distribution of water resources is enhanced.

  9. Modelling spatial trends in sorghum breeding field trials using a two-dimensional P-spline mixed model.

    Science.gov (United States)

    Velazco, Julio G; Rodríguez-Álvarez, María Xosé; Boer, Martin P; Jordan, David R; Eilers, Paul H C; Malosetti, Marcos; van Eeuwijk, Fred A

    2017-07-01

    A flexible and user-friendly spatial method called SpATS performed comparably to more elaborate and trial-specific spatial models in a series of sorghum breeding trials. Adjustment for spatial trends in plant breeding field trials is essential for efficient evaluation and selection of genotypes. Current mixed model methods of spatial analysis are based on a multi-step modelling process where global and local trends are fitted after trying several candidate spatial models. This paper reports the application of a novel spatial method that accounts for all types of continuous field variation in a single modelling step by fitting a smooth surface. The method uses two-dimensional P-splines with anisotropic smoothing formulated in the mixed model framework, referred to as SpATS model. We applied this methodology to a series of large and partially replicated sorghum breeding trials. The new model was assessed in comparison with the more elaborate standard spatial models that use autoregressive correlation of residuals. The improvements in precision and the predictions of genotypic values produced by the SpATS model were equivalent to those obtained using the best fitting standard spatial models for each trial. One advantage of the approach with SpATS is that all patterns of spatial trend and genetic effects were modelled simultaneously by fitting a single model. Furthermore, we used a flexible model to adequately adjust for field trends. This strategy reduces potential parameter identification problems and simplifies the model selection process. Therefore, the new method should be considered as an efficient and easy-to-use alternative for routine analyses of plant breeding trials.

  10. Learning optimal spatially-dependent regularization parameters in total variation image denoising

    Science.gov (United States)

    Van Chung, Cao; De los Reyes, J. C.; Schönlieb, C. B.

    2017-07-01

    We consider a bilevel optimization approach in function space for the choice of spatially dependent regularization parameters in TV image denoising models. First- and second-order optimality conditions for the bilevel problem are studied when the spatially-dependent parameter belongs to the Sobolev space {{H}1}≤ft(Ω \\right) . A combined Schwarz domain decomposition-semismooth Newton method is proposed for the solution of the full optimality system and local superlinear convergence of the semismooth Newton method is verified. Exhaustive numerical computations are finally carried out to show the suitability of the approach.

  11. Fine Spatial Scale Variation of Soil Microbial Communities under European Beech and Norway Spruce

    Science.gov (United States)

    Nacke, Heiko; Goldmann, Kezia; Schöning, Ingo; Pfeiffer, Birgit; Kaiser, Kristin; Castillo-Villamizar, Genis A.; Schrumpf, Marion; Buscot, François; Daniel, Rolf; Wubet, Tesfaye

    2016-01-01

    The complex interactions between trees and soil microbes in forests as well as their inherent seasonal and spatial variations are poorly understood. In this study, we analyzed the effects of major European tree species (Fagus sylvatica L. and Picea abies (L.) Karst) on soil bacterial and fungal communities. Mineral soil samples were collected from different depths (0–10, 10–20 cm) and at different horizontal distances from beech or spruce trunks (0.5, 1.5, 2.5, 3.5 m) in early summer and autumn. We assessed the composition of soil bacterial and fungal communities based on 16S rRNA gene and ITS DNA sequences. Community composition of bacteria and fungi was most strongly affected by soil pH and tree species. Different ectomycorrhizal fungi (e.g., Tylospora) known to establish mutualistic associations with plant roots showed a tree species preference. Moreover, bacterial and fungal community composition showed spatial and seasonal shifts in soil surrounding beech and spruce. The relative abundance of saprotrophic fungi was higher at a depth of 0–10 vs. 10–20 cm depth. This was presumably a result of changes in nutrient availability, as litter input and organic carbon content decreased with soil depth. Overall bacterial community composition showed strong variations under spruce with increasing distance from the tree trunks, which might be attributed in part to higher fine root biomass near spruce trunks. Furthermore, overall bacterial community composition was strongly affected by season under deciduous trees. PMID:28066384

  12. EFFECT OF INDUSTRIAL POLLUTION ON THE SPATIAL VARIATION OF SURFACE WATER QUALITY

    Directory of Open Access Journals (Sweden)

    Islam Mir Sujaul

    2013-01-01

    Full Text Available Surface water quality deterioration is the impact of anthropogenic activities at the study areas due to rapid industrialization. The study was done to know the spatial variation of the water quality of the Tunggak River and surrounding area because of industrial activities. In-situ parameters and ex-situ data of chemical, bio-chemical parameters and heavy metals were collected monthly to fulfill the objectives. The samples were collected from 10 selected stations and analyses were carried out using standard methods. Heavy metals were determined by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS. SPSS statistical software was used for data analysis. The results of the study revealed that industrial effluents were the major source of pollutants and caused of spatial variation among the stations. Less amount of Dissolved Oxygen (DO and higher concentration of Chemical Oxygen Demand (COD, Biochemical Oxygen Demand (BOD, ammoniacal-nitrogen and heavy metals made the water un-usable except irrigation. Analyzed surface water was classified based on Department of Environment-Water Quality Index (DOE-WQI Malaysia and found that the maximum stations except lower and uppermost were in class IV (highly polluted. Pollution rate was higher in the middle stations due to large number of industries were located in the middle and they discharged all their effluents in the river stream. Due to tidal interference in the lower stream and minimum industry in the upper stream pollution was less in those stations.

  13. Population ecology of Paepalanthus polyanthus (Bong. Kunth: temporal variation in the pattern of spatial distribution

    Directory of Open Access Journals (Sweden)

    Tânia Tarabini Castellani

    2004-11-01

    Full Text Available The temporal variation in density and pattern of spatial distribution of Paepalanthus polyanthus (BONG. Kunth (Eriocaulaceae were evaluated at a determinate sand dune. This study was carried out over a period of five years, at three permanent plots of 25m2 in a sand dune slack at Joaquina Beach, Florianópolis, SC, Brazil. There were strong density fluctuations throughout these years. In areas 1, 2 and 3, the densities changed from 10.4, 2.2 and 1.8 plants/m2 in December 1986 to 75.8, 11.4 and 45.6 plants/m2 in December 1991. Area 3, situated on an elevated site, presented greater variation in density, with no live plants in December 1989 and 102.2 plants/m2 at the recruitment observed in May 1990. Despite these density fluctuations, the pattern of spatial distribution was always aggregated (Id>1, P<0.05. The greatest Id values occurred in periods of low density and not in those of high density, associated with seedling recruitment. Factors such as high seed production with low dispersal, massive germination in moit years and a comparatively high death rate of seedlings at sites more subject to flooding or more distant from the water table proved themselves able to promote this aggregate pattern and increase it during plant development.

  14. Spatial variation in level of agricultural development in Bulandshahr district of western Uttar Pradesh (India

    Directory of Open Access Journals (Sweden)

    Gomatee Singh

    2012-06-01

    Full Text Available In the present paper an attempt has been made to find out the spatial variation in the adaptation of improved agricultural practices to ascertain the level of agricultural development in Bulandshahr district of western Uttar Pradesh. The spatial variation of agricultural development is determined with the help of nine variables viz. net sown area, irrigated area, cropping intensity, crops productivity, area under HYV, agricultural labourers, role of banks and agricultural machinery. Beside this, the development of blocks are taken with their respective categories viz. high, medium and low on the basis of scores (like mean SD of these variables. These analyses have been carried out by transforming and combining the data related to nine variables, using ‘Z’ score to get the composite score. On the basis of Composite Score, developments of blocks have been again categorized in to three categories i.e. high, medium and low. Results of the aforesaid analysis shows that the modern technological inputs have reciprocal relationship with agricultural development in the study area.

  15. Constraints on field theoretical models for variation of the fine structure constant

    Science.gov (United States)

    Steinhardt, Charles L.

    2005-02-01

    Recent theoretical ideas and observational claims suggest that the fine structure constant α may be variable. We examine a spectrum of models in which α is a function of a scalar field. Specifically, we consider three scenarios: oscillating α, monotonic time variation of α, and time-independent α that is spatially varying. We examine the constraints imposed upon these theories by cosmological observations, particle detector experiments, and “fifth force” experiments. These constraints are very strong on models involving oscillation but cannot compete with bounds from the Oklo subnuclear reactor on models with monotonic timelike variation of α. One particular model with spatial variation is consistent with all current experimental and observational measurements, including those from two seemingly conflicting measurements of the fine structure constant using the many multiplet method on absorption lines.

  16. Modeling of microscale variations in methane fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Kettunen, A.

    2002-07-01

    The current study analyzes the different modes of variation in methane fluxes from different microsites of a boreal mire. The results emphasize the importance of microsite characteristics, water table and vegetation cover for methane fluxes. Water level affects the moisture and oxygen profiles in peat matrix which are reflected to methane production and oxidation rates and the corresponding microbial populations. Vascular plants promote methane production by providing substrates in the form of root exudates and fine root litter, enhance methane oxidation by transporting oxygen to water saturated peat layers and accelerate methane transport by liberating methane from peat to the atmosphere via the aerenchymous tissue. The model presented in this study connects the methane fluxes to the seasonal photosynthetic cycle of plants at the microsite level while the thermal and hydrological conditions in peat are used as an operational framework. Overall, the model dynamically combines the microbial processes in peat to changing environmental factors in the level of peatland ecosystem. Sensitivity analysis of the model reveals the importance of substrate supply to methane fluxes. Furthermore, the model outcome is sensitive to increased capability of the vascular plants to transport oxygen downwards. Lack of oxygen and partly methane keep methane oxidation at a very low level. Any changes in model parameters or environmental conditions that compensate for these lacks have a remarkable decreasing effect on simulated flux. Simulated methane flux decreases considerably if the duration of simulated dry period increases, threshold for a dramatic change lying between 4 and 6 weeks of drought. Increase in air temperature enhances methane flux especially if the effect of increased temperature on gross primary production is taken into account. (orig.)

  17. An API for Integrating Spatial Context Models with Spatial Reasoning Algorithms

    DEFF Research Database (Denmark)

    Kjærgaard, Mikkel Baun

    2006-01-01

    The integration of context-aware applications with spatial context models is often done using a common query language. However, algorithms that estimate and reason about spatial context information can benefit from a tighter integration. An object-oriented API makes such integration possible and ...... modeling. The utility of the API is evaluated in several real-world cases from an indoor location system, and spans several types of spatial reasoning algorithms.......The integration of context-aware applications with spatial context models is often done using a common query language. However, algorithms that estimate and reason about spatial context information can benefit from a tighter integration. An object-oriented API makes such integration possible...

  18. Functional-Coefficient Spatial Durbin Models with Nonparametric Spatial Weights: An Application to Economic Growth

    Directory of Open Access Journals (Sweden)

    Mustafa Koroglu

    2016-02-01

    Full Text Available This paper considers a functional-coefficient spatial Durbin model with nonparametric spatial weights. Applying the series approximation method, we estimate the unknown functional coefficients and spatial weighting functions via a nonparametric two-stage least squares (or 2SLS estimation method. To further improve estimation accuracy, we also construct a second-step estimator of the unknown functional coefficients by a local linear regression approach. Some Monte Carlo simulation results are reported to assess the finite sample performance of our proposed estimators. We then apply the proposed model to re-examine national economic growth by augmenting the conventional Solow economic growth convergence model with unknown spatial interactive structures of the national economy, as well as country-specific Solow parameters, where the spatial weighting functions and Solow parameters are allowed to be a function of geographical distance and the countries’ openness to trade, respectively.

  19. Spatial and temporal variation in evacuee risk perception throughout the evacuation and return-entry process.

    Science.gov (United States)

    Siebeneck, Laura K; Cova, Thomas J

    2012-09-01

    Developing effective evacuation and return-entry plans requires understanding the spatial and temporal dimensions of risk perception experienced by evacuees throughout a disaster event. Using data gathered from the 2008 Cedar Rapids, Iowa Flood, this article explores how risk perception and location influence evacuee behavior during the evacuation and return-entry process. Three themes are discussed: (1) the spatial and temporal characteristics of risk perception throughout the evacuation and return-entry process, (2) the relationship between risk perception and household compliance with return-entry orders, and (3) the role social influences have on the timing of the return by households. The results indicate that geographic location and spatial variation of risk influenced household risk perception and compliance with return-entry plans. In addition, sociodemographic characteristics influenced the timing and characteristics of the return groups. The findings of this study advance knowledge of evacuee behavior throughout a disaster and can inform strategies used by emergency managers throughout the evacuation and return-entry process. © 2012 Society for Risk Analysis.

  20. Spatial variation in coral reef fish and benthic communities in the central Saudi Arabian Red Sea

    KAUST Repository

    Khalil, Maha T.

    2017-06-06

    Local-scale ecological information is critical as a sound basis for spatial management and conservation and as support for ongoing research in relatively unstudied areas. We conducted visual surveys of fish and benthic communities on nine reefs (3–24 km from shore) in the Thuwal area of the central Saudi Arabian Red Sea. Fish biomass increased with increasing distance from shore, but was generally low compared to reefs experiencing minimal human influence around the world. All reefs had a herbivore-dominated trophic structure and few top predators, such as sharks, jacks, or large groupers. Coral cover was considerably lower on inshore reefs, likely due to a 2010 bleaching event. Community analyses showed inshore reefs to be characterized by turf algae, slower-growing corals, lower herbivore diversity, and highly abundant turf-farming damselfishes. Offshore reefs had more planktivorous fishes, a more diverse herbivore assemblage, and faster-growing corals. All reefs appear to be impacted by overfishing, and inshore reefs seem more vulnerable to thermal bleaching. The study provides a description of the spatial variation in biomass and community structure in the central Saudi Arabian Red Sea and provides a basis for spatial prioritization and subsequent marine protected area design in Thuwal.

  1. Spatial variation in coral reef fish and benthic communities in the central Saudi Arabian Red Sea

    Directory of Open Access Journals (Sweden)

    Maha T. Khalil

    2017-06-01

    Full Text Available Local-scale ecological information is critical as a sound basis for spatial management and conservation and as support for ongoing research in relatively unstudied areas. We conducted visual surveys of fish and benthic communities on nine reefs (3–24 km from shore in the Thuwal area of the central Saudi Arabian Red Sea. Fish biomass increased with increasing distance from shore, but was generally low compared to reefs experiencing minimal human influence around the world. All reefs had a herbivore-dominated trophic structure and few top predators, such as sharks, jacks, or large groupers. Coral cover was considerably lower on inshore reefs, likely due to a 2010 bleaching event. Community analyses showed inshore reefs to be characterized by turf algae, slower-growing corals, lower herbivore diversity, and highly abundant turf-farming damselfishes. Offshore reefs had more planktivorous fishes, a more diverse herbivore assemblage, and faster-growing corals. All reefs appear to be impacted by overfishing, and inshore reefs seem more vulnerable to thermal bleaching. The study provides a description of the spatial variation in biomass and community structure in the central Saudi Arabian Red Sea and provides a basis for spatial prioritization and subsequent marine protected area design in Thuwal.

  2. Spatial variation in environmental noise and air pollution in New York City.

    Science.gov (United States)

    Kheirbek, Iyad; Ito, Kazuhiko; Neitzel, Richard; Kim, Jung; Johnson, Sarah; Ross, Zev; Eisl, Holger; Matte, Thomas

    2014-06-01

    Exposure to environmental noise from traffic is common in urban areas and has been linked to increased risks of adverse health effects including cardiovascular disease. Because traffic sources also produce air pollutants that increase the risk of cardiovascular morbidity, associations between traffic exposures and health outcomes may involve confounding and/or synergisms between air pollution and noise. While prior studies have characterized intraurban spatial variation in air pollution in New York City (NYC), limited data exists on the levels and spatial variation in noise levels. We measured 1-week equivalent continuous sound pressure levels (Leq) at 56 sites during the fall of 2012 across NYC locations with varying traffic intensity and building density that are routinely monitored for combustion-related air pollutants. We evaluated correlations among several noise metrics used to characterize noise exposures, including Leq during different time periods (night, day, weekday, weekend), Ldn (day-night noise), and measures of intermittent noise defined as the ratio of peak levels to median and background levels. We also examined correlations between sound pressure levels and co-located simultaneous measures of nitric oxide (NO), nitrogen dioxide (NO2), fine particulate matter (PM2.5), and black carbon (BC) as well as estimates of traffic and building density around the monitoring sites. Noise levels varied widely across the 56 monitoring sites; 1-week Leq varied by 21.6 dBA (range 59.1-80.7 dBA) with the highest levels observed during the weekday, daytime hours. Indices of average noise were well correlated with each other (r > 0.83), while indices of intermittent noise were not well correlated with average noise levels (r air pollutants suggest the possibility for confounding and/or synergism in intraurban epidemiological studies of traffic-related health effects. The different spatial pattern of intermittent noise compared to average noise level may suggest

  3. Long term (1997-2014) spatial and temporal variations in nitrogen in Dongting Lake, China.

    Science.gov (United States)

    Tian, Zebin; Zheng, Binghui; Wang, Lijing; Li, Liqiang; Wang, Xing; Li, Hong; Norra, Stefan

    2017-01-01

    In order to protect the water quality of Dongting Lake, it is significant to find out its nitrogen pollution characteristics. Using long-term monthly to seasonally data (1997-2014), we investigated the spatial and temporal variations in nitrogen in Dongting Lake, the second largest freshwater lake in China. The average concentrations of total nitrogen (TN) in the eastern, southern, and western parts of the lake were 1.77, 1.56, and 1.35 mg/L, respectively, in 2014. TN pollution was generally worse in the southern area than in the western area. Concentrations showed temporal variation, and were significantly higher during the dry season than during the wet season. Based on the concentration and growth rate of TN, three different stages were identified in the long term lake data, from 1997 to 2002, from 2003 to 2008, and from 2009 to 2014, during which the concentrations and the growth rate ranged from 1.09-1.51 mg/L and 22.09%-40.03%, 1.05-1.57 mg/L and -9.05%-7.74%, and 1.68-2.02 mg/L and 57.99%-60.41%, respectively. The main controls on the lake water TN concentrations were the quality and quantity of the lake inflows, spatial and temporal variations in hydrodynamic conditions within the lake (flow velocity, flow direction), and point and nonpoint inputs from human activities. Diffuse nutrient losses from agricultural land are a significant contributor. As a priority, the local government should aim to control the pollutant inputs from upstream and non-point nutrient losses from land.

  4. Seasonal and spatial variations of snow chemistry on Mount Logan, Yukon, Canada

    Science.gov (United States)

    Goto-Azuma, Kumiko; Koerner, Roy M.; Demuth, Michael N.; Watanabe, Okitsugu

    Three ice cores were recovered on or near Mount Logan, Yukon, Canada, at 3017, 4135 and 5340 m a.s.l. in 2002. Prior to ice-core drilling, we collected snow-pit and shallow core samples from Mount Logan in 2001 to study seasonal and spatial variations of snow chemistry. We dug snow pits at six sites between 2420 and 5340 m a.s.l. before the beginning of the melt season, with the exception of a pit at 3180 m a.s.l., where the melt season had just started but had affected only the near-surface stratigraphy. Three of the pits were extended deeper with a shallow core. The snow-pit and core samples were analyzed for ion chemistry and δ18O. A series of depth profiles of ions and δ18O shows spatial variations, though characteristic peaks can usually be traced across all the profiles. Concentrations and deposition fluxes of Na+ and Cl-, which are mainly of sea-salt origin, decrease with altitude. On the other hand, deposition fluxes of NO3-, SO42-, Ca2+ and NH4+ show a weak positive relationship with elevation below the summit plateau. Stable isotopes (δ18O) decrease with altitude, with a distinctive jump between 3200 and 4500 m a.s.l., as was reported previously. Stable isotopes (δ18O), Cl-, CH3SO3-(MSA), Na+ and Ca2+ show clear seasonal variations, which would enable us to date the cores by annual-layer counting.

  5. Modelling spatial vagueness based on type-2 fuzzy set

    Institute of Scientific and Technical Information of China (English)

    DU Guo-ning; ZHU Zhong-ying

    2006-01-01

    The modelling and formal characterization of spatial vagueness plays an increasingly important role in the implementation of Geographic Information System (GIS). The concepts involved in spatial objects of GIS have been investigated and acknowledged as being vague and ambiguous. Models and methods which describe and handle fuzzy or vague (rather than crisp or determinate) spatial objects, will be more necessary in GIS. This paper proposes a new method for modelling spatial vagueness based on type-2 fuzzy set, which is distinguished from the traditional type-1 fuzzy methods and more suitable for describing and implementing the vague concepts and objects in GIS.

  6. Spatial and temporal variation of emission inventories for historical anthropogenic NMVOCs in China

    Directory of Open Access Journals (Sweden)

    Y. Bo

    2008-06-01

    Full Text Available Multiyear emission inventories of anthropogenic NMVOCs in China for 1980–2005 were compiled based on time-varying statistical data, literature surveyed and model calculated emission factors, and were gridded at a high spatial resolution of 40 km×40 km using the GIS methodology. Chinese NMVOCs emissions had increased by 4.3 times at an annual average rate of 10.7% from 3.92 Tg in 1980 to 16.5 Tg in 2005. Vehicles, biomass burning, industrial processes, fossil fuel combustion, solvent utilization, and storage and transport generated 5.49 Tg, 3.91 Tg, 2.76 Tg, 1.98 Tg, 1.87 Tg, and 0.55 Tg of NMVOCs, respectively. Motorcycles, biofuel burning, heavy-duty vehicles, synthetic fibre production, biomass open burning, and industrial and commercial consumption were primary emission sources. Besides, from 1980 to 2005, vehicle emission increased notably from 6% to 33%, along with a slight increase for fossil fuel combustion from 9% to 12% and for industrial processes from 11% to 17%. Meanwhile, biomass burning emission decreased from 41% to 23%, along with the decrease of storage and transport and solvent utilization from 9% to 3% and from 28% to 11%, respectively. Varieties of NMVOCs emissions coincided well with China's economic growth. Conversions in economic structure and adjustment of fuel consumption structure in China during the period were the reasons for conspicuous variation of source contributions. The developed eastern and coastal regions produced more emissions than the relatively underdeveloped western and inland regions. Particularly, southeastern, northern, and central China covering 35% of China's territory, generated 59% of the total emissions, while the populous capital cities covering merely 4.5% of China's territory, accounted for 25% of the national emissions. Moreover, rural areas also experienced emission growth during the past two and a half decades, the reason of which was transfer of emission-intensive plants

  7. SPATIAL AND TEMPORAL VARIATIONS OF EVAPORATION OVER SOUTH CHINA IN AUTUMN

    Institute of Scientific and Technical Information of China (English)

    XIAO Wei-jun; LIANG Yu-qiong; HE Ju-xiong; CHEN Bing-hong

    2008-01-01

    The spatial and temporal variations of the instrument-based evaporation and actual evaporation in autumn during a 45-year period fi'om 1960 to 2004 are studied using the observation data from 66 stations over South China. The results reveal that there are two main anomalous centers of the instrument-based evaporation in autumn in the central and northwestern parts of South China respectively. The instrument-based evaporation over the central part of South China in autumn experiences not only a decreasing trend but also a main interdecadal variation. The solar radiation is best correlated with the instrument-based evaporation among all affecting factors. For the actual evaporation, two main anomalous centers are located at the central and western parts of the South China respectively. The actual evaporation over the two regions illustrates an interannual variation. Among the affecting factors, precipitation is the most remarkable. The actual evaporation is usually 40 percent of the instrument-based one, and the overall rate has a slightly increasing trend from the southern part to the northern part of the South China in autumn.

  8. Using multilevel spatial models to understand salamander site occupancy patterns after wildfire

    Science.gov (United States)

    Chelgren, N.D.; Adams, M.J.; Bailey, L.L.; Bury, R.B.

    2011-01-01

    Studies of the distribution of elusive forest wildlife have suffered from the confounding of true presence with the uncertainty of detection. Occupancy modeling, which incorporates probabilities of species detection conditional on presence, is an emerging approach for reducing observation bias. However, the current likelihood modeling framework is restrictive for handling unexplained sources of variation in the response that may occur when there are dependence structures such as smaller sampling units that are nested within larger sampling units. We used multilevel Bayesian occupancy modeling to handle dependence structures and to partition sources of variation in occupancy of sites by terrestrial salamanders (family Plethodontidae) within and surrounding an earlier wildfire in western Oregon, USA. Comparison of model fit favored a spatial N-mixture model that accounted for variation in salamander abundance over models that were based on binary detection/non-detection data. Though catch per unit effort was higher in burned areas than unburned, there was strong support that this pattern was due to a higher probability of capture for individuals in burned plots. Within the burn, the odds of capturing an individual given it was present were 2.06 times the odds outside the burn, reflecting reduced complexity of ground cover in the burn. There was weak support that true occupancy was lower within the burned area. While the odds of occupancy in the burn were 0.49 times the odds outside the burn among the five species, the magnitude of variation attributed to the burn was small in comparison to variation attributed to other landscape variables and to unexplained, spatially autocorrelated random variation. While ordinary occupancy models may separate the biological pattern of interest from variation in detection probability when all sources of variation are known, the addition of random effects structures for unexplained sources of variation in occupancy and detection

  9. Spatial and temporal variation in pH, alkalinity and conductivity in surface runoff and groundwater for the Upper River Severn catchment

    Directory of Open Access Journals (Sweden)

    T. Hill

    1997-01-01

    Full Text Available Measurements of pH, alkalinity and electrical conductivity are used to examine the extent of the spatial and temporal variation in stream and ground water chemistry for the Upper Severn catchment, Plynlimon. Wide temporal variations in stream waters broadly reflect flow conditions and complex soil and ground water interactions but not soil type, land usage or geology. The results have major implications for the use of critical load analysis and the development and application of models in upland catchments. They point to the value of field measurements for assessing the environmental management of upland catchments, rather than the present use of over simplistic or inappropriate models.

  10. Book review: Statistical Analysis and Modelling of Spatial Point Patterns

    DEFF Research Database (Denmark)

    Møller, Jesper

    2009-01-01

    Statistical Analysis and Modelling of Spatial Point Patterns by J. Illian, A. Penttinen, H. Stoyan and D. Stoyan. Wiley (2008), ISBN 9780470014912......Statistical Analysis and Modelling of Spatial Point Patterns by J. Illian, A. Penttinen, H. Stoyan and D. Stoyan. Wiley (2008), ISBN 9780470014912...

  11. Proximal soil sensing to parameterize spatial environmental modeling

    Science.gov (United States)

    Spatially explicit models are important tools to understand the effects of the interaction of management and landscape factors on water and soil quality. One challenge to application of such models is the need to know spatially-distributed values for input parameters. Some such data can come from av...

  12. Recent developments in spatial analysis spatial statistics, behavioural modelling, and computational intelligence

    CERN Document Server

    Getis, Arthur

    1997-01-01

    In recent years, spatial analysis has become an increasingly active field, as evidenced by the establishment of educational and research programs at many universities. Its popularity is due mainly to new technologies and the development of spatial data infrastructures. This book illustrates some recent developments in spatial analysis, behavioural modelling, and computational intelligence. World renown spatial analysts explain and demonstrate their new and insightful models and methods. The applications are in areas of societal interest such as the spread of infectious diseases, migration behaviour, and retail and agricultural location strategies. In addition, there is emphasis on the uses of new technologoies for the analysis of spatial data through the application of neural network concepts.

  13. Consequences of spatial autocorrelation for niche-based models

    DEFF Research Database (Denmark)

    Segurado, P.; Araújo, Miguel B.; Kunin, W. E.

    2006-01-01

    variables, as measured by Moran's I, was analysed and compared between models. The effects of systematic subsampling of the data set and the inclusion of a contagion term to deal with spatial autocorrelation in models were assessed with projections made with GLM, as it was with this method that estimates...... were vulnerable to the effects of spatial autocorrelation. 5.  The procedures utilized to reduce the effects of spatial autocorrelation had varying degrees of success. Subsampling was partially effective in avoiding the inflation effect, whereas the inclusion of a contagion term fully eliminated......1.  Spatial autocorrelation is an important source of bias in most spatial analyses. We explored the bias introduced by spatial autocorrelation on the explanatory and predictive power of species' distribution models, and make recommendations for dealing with the problem. 2.  Analyses were based...

  14. Beech bark necrosis: partitioning the environmental and spatial variation of the damage severity in Central and South-Eastern Europe

    Directory of Open Access Journals (Sweden)

    Benjamín Jarčuška

    2013-11-01

    Full Text Available The beech bark necrosis (BBN infestation severity of Europeanbeech (Fagus sylvatica L. was assessed in regions of Central (CE andSouth-Eastern Europe (SE. Altogether more than 10,000 trees were sampled at 114 sites. Using variation partitioning method, we examined the pure and shared effects of stand, site, climate and spatial sets of variables on mean BBN severity. Our rating included (i the whole stand, (ii tree social status classes, (iii canopy (C and (iv understory (U trees separately. We found that C trees were less affected by BBN than sub-canopy and U trees in both regions. There were found inter-regional differences in amount of explained variability (25.4–73.9% for whole stand BBN and in the sensitivity of C and U trees to the environmental gradients. The analysisrevealed that the climate and spatial variables followed by stand variables had the largest marginal effects on mean BBN severity in all models, while the site set of variables had the weakest one. More than half of the explained variation was shared among four sets of variables in SE, contrary to CE. Except to U trees in SE, the effect of climate – pure or spatially structured – remained the highest also after partitioning of variance; more in SE than in CE. Taking into account positive association between mean annual temperature and mean BBN severity in C trees in SE, reinforced negative effect of climate change on the necrosis might be expected to be more seriousmainly in low situated beech forests there. Promoting the tree speciesdiversity in forested areas with higher incidence of beech bark necrosis, i.e. in low altitudes in SE, could reduce the susceptibility of forests to the necrosis at regional level in the future. For better understanding of the relative importance of environmental and spatial variables on BBN severity, further research performed on finer spatial scale (extent and grain is necessary, along with accounting for pathogens involved in the

  15. Variation in the macrofaunal community over large temporal and spatial scales in the southern Yellow Sea

    Science.gov (United States)

    Xu, Yong; Sui, Jixing; Yang, Mei; Sun, Yue; Li, Xinzheng; Wang, Hongfa; Zhang, Baolin

    2017-09-01

    To detect large, temporal- and spatial-scale variations in the macrofaunal community in the southern Yellow Sea, data collected along the western, middle and eastern regions of the southern Yellow Sea from 1958 to 2014 were organized and analyzed. Statistical methods such as cluster analysis, non-metric multidimensional scaling ordination (nMDS), permutational multivariate analysis of variance (PERMANOVA), redundancy analysis (RDA) and canonical correspondence analysis (CCA) were applied. The abundance of polychaetes increased in the western region but decreased in the eastern region from 1958 to 2014, whereas the abundance of echinoderms showed an opposite trend. For the entire macrofaunal community, Margalef's richness (d), the Shannon-Wiener index (H‧) and Pielou's evenness (J‧) were significantly lower in the eastern region when compared with the other two regions. No significant temporal differences were found for d and H‧, but there were significantly lower values of J‧ in 2014. Considerable variation in the macrofaunal community structure over the past several decades and among the geographical regions at the species, genus and family levels were observed. The species, genera and families that contributed to the temporal variation in each region were also identified. The most conspicuous pattern was the increase in the species Ophiura sarsii vadicola in the eastern region. In the western region, five polychaetes (Ninoe palmata, Notomastus latericeus, Paralacydonia paradoxa, Paraprionospio pinnata and Sternaspis scutata) increased consistently from 1958 to 2014. The dominance curves showed that both the species diversity and the dominance patterns were relatively stable in the western and middle regions. Environmental parameters such as depth, temperature and salinity could only partially explain the observed biological variation in the southern Yellow Sea. Anthropogenic activities such as demersal fishing and other unmeasured environmental variables

  16. Emergent universe in spatially flat cosmological model

    CERN Document Server

    Zhang, Kaituo; Yu, Hongwei

    2013-01-01

    The scenario of an emergent universe provides a promising resolution to the big bang singularity in universes with positive or negative spatial curvature. It however remains unclear whether the scenario can be successfully implemented in a spatially flat universe which seems to be favored by present cosmological observations. In this paper, we study the stability of Einstein static state solutions in a spatially flat Shtanov-Sahni braneworld scenario. With a negative dark radiation term included and assuming a scalar field as the only matter energy component, we find that the universe can stay at an Einstein static state past eternally and then evolve to an inflation phase naturally as the scalar field climbs up its potential slowly. In addition, we also propose a concrete potential of the scalar field that realizes this scenario.

  17. Spatial-Temporal Variations of Chlorophyll-a in the Adjacent Sea Area of the Yangtze River Estuary Influenced by Yangtze River Discharge

    Directory of Open Access Journals (Sweden)

    Ying Wang

    2015-05-01

    Full Text Available Carrying abundant nutrition, terrigenous freshwater has a great impact on the spatial and temporal heterogeneity of phytoplankton in coastal waters. The present study analyzed the spatial-temporal variations of Chlorophyll-a (Chl-a concentration under the influence of discharge from the Yangtze River, based on remotely sensed Chl-a concentrations. The study area was initially zoned to quantitatively investigate the spatial variation patterns of Chl-a. Then, the temporal variation of Chl-a in each zone was simulated by a sinusoidal curve model. The results showed that in the inshore waters, the terrigenous discharge was the predominant driving force determining the pattern of Chl-a, which brings the risk of red tide disasters; while in the open sea areas, Chl-a was mainly affected by meteorological factors. Furthermore, a diversity of spatial and temporal variations of Chl-a existed based on the degree of influences from discharge. The diluted water extended from inshore to the east of Jeju Island. This process affected the Chl-a concentration flowing through the area, and had a potential impact on the marine environment. The Chl-a from September to November showed an obvious response to the discharge from July to September with a lag of 1 to 2 months.

  18. Tidal and spatial variations of DI13C and aquatic chemistry in a temperate tidal basin during winter time

    Science.gov (United States)

    Winde, V.; Böttcher, M. E.; Escher, P.; Böning, P.; Beck, M.; Liebezeit, G.; Schneider, B.

    2014-01-01

    Here, the pelagic carbonate system and the δ13C signature of dissolved inorganic carbonate (DIC) were investigated in a tidal basin of the southern North Sea, the Jade Bay, with respect to tidal cycles and a transect towards the North Sea in winter time (January and November, 2010). Physical parameters, major and trace elements, and nutrient concentrations were considered, too. Primary production and pelagic organic matter respiration were negligible during winter time. Both, the compositional variations on the transects as well as during the tidal cycles indicate the mixing of North Sea with fresh water. The combined spatial co-variations of different parameters indicate an introduction of fresh water that was enriched in DI12C, metabolites (e.g., ammonia), protons, and dissolved redox-sensitive elements (e.g., Mn2 +). During the January campaign, the discharge via the flood gates was limited due to ice cover of the hinterland drainage ditches, allowing for an observation of tidal variations without significant mixing contributions from surface water discharges. Considering a binary mixing model with North Sea and fresh water as end-members, the extrapolated fresh water end-member composition for this campaign is estimated to contain about 3.8 mmol/kg DIC (δ13C ≈ - 10 ± 1‰ vs. VPDB), and enhanced concentrations of NH4+, Mn2 +, and protons compared to North Sea water. The fast temporal response of dissolved geochemical tracers on tidal variations in the Jade Bay indicates a continuous supply of a fresh water component. The measured composition of fresh waters entering the Jade Bay via flood gates (end of October, 2010) did not match the values estimated by the binary mixing model. Therefore, the overall fresh water component likely is a mixture between sources originating from flood gates and (in January) dominating submarine groundwater discharge entering the Jade Bay. This model is consistent with the results obtained during the November campaign, when a

  19. A formal model for access control with supporting spatial context

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong; HE YePing; SHI ZhiGuo

    2007-01-01

    There is an emerging recognition of the importance of utilizing contextual information in authorization decisions. Controlling access to resources in the field of wireless and mobile networking require the definition of a formal model for access control with supporting spatial context. However, traditional RBAC model does not specify these spatial requirements. In this paper, we extend the existing RBAC model and propose the SC-RBAC model that utilizes spatial and location-based information in security policy definitions. The concept of spatial role is presented,and the role is assigned a logical location domain to specify the spatial boundary.Roles are activated based on the current physical position of the user which obtained from a specific mobile terminal. We then extend SC-RBAC to deal with hierarchies, modeling permission, user and activation inheritance, and prove that the hierarchical spatial roles are capable of constructing a lattice which is a means for articulate multi-level security policy and more suitable to control the information flow security for safety-critical location-aware information systems. Next, constrained SC-RBAC allows express various spatial separations of duty constraints,location-based cardinality and temporal constraints for specify fine-grained spatial semantics that are typical in location-aware systems. Finally, we introduce 9 invariants for the constrained SC-RBAC and its basic security theorem is proven. The constrained SC-RBAC provides the foundation for applications in need of the constrained spatial context aware access control.

  20. Modeling the spatial reach of the LFP

    DEFF Research Database (Denmark)

    Lindén, Henrik; Tetzlaff, Tom; Potjans, Tobias C

    2011-01-01

    The local field potential (LFP) reflects activity of many neurons in the vicinity of the recording electrode and is therefore useful for studying local network dynamics. Much of the nature of the LFP is, however, still unknown. There are, for instance, contradicting reports on the spatial extent...... distribution, and the correlation in synaptic activity. For uncorrelated activity, the LFP represents cells in a small region (within a radius of a few hundred micrometers). If the LFP contributions from different cells are correlated, the size of the generating region is determined by the spatial extent...

  1. Spatial and temporal variations of water quality in Cao-E River of eastern China

    Institute of Scientific and Technical Information of China (English)

    CHEN Ding-jiang; LU Jun; YUAN Shao-feng; JIN Shu-quan; SHEN Ye-na

    2006-01-01

    Evaluation and analysis of water quality variations were performed with integrated consideration of water quality parameters, hydrological-meteorologic and anthropogenic factors in Cao-E River, Zhejiang Province of China. Cao-E River system has been polluted and the water quality of some reaches are inferior to Grade V according to National Surface Water Quality Standard of China (GB2002). However, mainly polluted indices of each tributary and mainstream are different. Total nitrogen (TN) and total phosphorus (TP) in the water are the main polluted indices for mainstream that varies from 1.52 to 45.85 mg/L and 0.02 to 4.02 mg/L,respectively. TN is the main polluted indices for Sub-watershed Ⅰ, Ⅱ, Ⅳ and Ⅴ (0.76 to 18.27 mg/L). BOD5 (0.36 to 289.5 mg/L),CODMn (0.47 to 78.86 mg/L), TN (0.74 to 31.09 mg/L) and TP (0 to 3.75 mg/L) are the main polluted indices for Sub-watershed Ⅲ.There are tow pollution types along the river including nonpoint source pollution and point source pollution types. Remarkably temporal variations with a few spatial variations occur in nonpoint pollution type reaches (including mainstream, Sub-watershed Ⅰ and Ⅱ) that mainly drained by arable field and/or dispersive rural dwelling district, and the maximum pollutant concentration appears in flooding seasons. It implied that the runoff increases the pollutant concentration of the water in the nonpoint pollution type reaches. On the other hand, remarkably spatial variations occur in the point pollution type reaches (include Sub-watershed Ⅲ, Ⅳ and Ⅴ) and the maximum pollutant concentration appears in urban reaches. The runoff always decreases the pollutant concentration of the river water in the seriously polluted reaches that drained by industrial point sewage. But for the point pollution reaches resulted from centralized town domestic sewage pipeline and from frequent shipping and digging sands, rainfall always increased the concentration of pollutant (TN) in the river water

  2. Spatial variations of effective elastic thickness of the Lithosphere in the Southeast Asia regions

    Science.gov (United States)

    Shi, Xiaobin; Kirby, Jon; Yu, Chuanhai; Swain, Chris; Zhao, Junfeng

    2016-04-01

    The effective elastic thickness Te corresponds to the thickness of an idealized elastic beam that would bend similarly to the actual lithosphere under the same applied loads, and could provide important insight into rheology and state of stress. Thus, it is helpful to improve our understanding of the relationship between tectonic styles, distribution of earthquakes and lithospheric rheology in various tectonic settings. The Southeast Asia, located in the southeastern part of the Eurasian Plate, comprises a complex collage of continental fragments, volcanic arcs, and suture zones and marginal oceanic basins, and is surrounded by tectonically active margins which exhibit intense seismicity and volcanism. The Cenozoic southeastward extrusion of the rigid Indochina Block due to the Indo-Asian collision resulted in the drastic surface deformation in the western area. Therefore, a high resolution spatial variation map of Te might be a useful tool for the complex Southeast Asia area to examine the relationships between surface deformation, earthquakes, lithospheric structure and mantle dynamics. In this study, we present a high-resolution map of spatial variations of Te in the Southeast Asia area using the wavelet method, which convolves a range of scaled wavelets with the two data sets of Bouguer gravity anomaly and topography. The topography and bathymetry grid data was extracted from the GEBCO_08 Grid of GEBCO digital atlas. The pattern of Te variations agrees well with the tectonic provinces in the study area. On the whole, low lithosphere strength characterizes the oceanic basins, such as the South China Sea, the Banda sea area, the Celebes Sea, the Sulu Sea and the Andaman Sea. Unlike the oceanic basins, the continental fragments show a complex pattern of Te variations. The Khorat plateau and its adjacent area show strong lithosphere characteristics with a Te range of 20-50 km, suggesting that the Khorat plateau is the strong core of the Indochina Block. The West

  3. Spatial and Temporal Variations in Interstellar Absorption toward HD 72127AB

    CERN Document Server

    Welty, Daniel E; Hobbs, L M

    2008-01-01

    New optical spectra of Ca II and Na I toward HD 72127AB provide additional evidence for both spatial and temporal variations in the complex interstellar absorption along the two sight lines; archival UV spectra yield information on the abundances, depletions, and physical conditions in the gas toward HD 72127A. Similarities in the strengths of various tracers of interstellar material in the two lines of sight suggest that the total hydrogen column densities [N(H) ~ 2.5 x 10^{20} cm^{-2}] and the depletions and ionization in the main components at low LSR velocities also are similar. Toward HD 72127A, the main components are relatively cool (T 5000 K) may be largely responsible for the enhanced abundances of those trace neutral species toward HD 72127B. If the main components toward HD 72127AB are associated with material in the Vela SNR, the differences in abundances and physical conditions occur on scales of about 1100 AU.

  4. Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait, China

    Institute of Scientific and Technical Information of China (English)

    HUANG Bangqin; LIN Xueju; HONG Huasheng

    2009-01-01

    The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70-209.2)×106 and (0.75-15.4)×106 cells/cm2 in the abundance, and 1.93-52.3 and 1.57-32.4 mgC/cm2 in the carbon biomass, for SYN and PEUK, respectively. The horizontal distributions of both groups were diurnal but heterogeneous in abundance, depending on the groups and layer of depths. Temperature is the key controlling factor for picophytoplankton distribution (especially in winter) in the Strait.

  5. Spatial and Temporal Variation of Water Quality in the Bertam Catchment, Cameron Highlands, Malaysia.

    Science.gov (United States)

    Rasul, G

    2016-12-16

    The spatio-temporal variability of water quality associated with anthropogenic activities was studied for the Bertam River and its main tributaries within the Bertam Catchment, Cameron Highlands, Malaysia. A number of physico-chemical parameters of collected samples were analyzed to evaluate their spatio-temporal variability. Non-parametric statistical analysis showed significant temporal and spatial differences (p<0.05) in most of the parameters across the Catchment. Parameters except DO and COD displayed higher values in rainy season.The higher concentration of total suspended solids was caused due to massive soil erosion and sedimentation. Seasonal variations in contaminant concentrations are largely affected by precipitation and anthropogenic influences.Untreated domestic wastewater discharge as well as agricultural runoff significantly influenced the water quality. Poor agricultural practices and development activities at slope areas also affected the water quality within the Catchment. The analytical results provided a basis for protection of river environments and ecological restoration in mountainous Bertam Catchment.

  6. Spatial-temporal variations in carbon dioxide levels in Ibadan, Nigeria.

    Science.gov (United States)

    Ana, Godson R; Ojelabi, Peju; Shendell, Derek G

    2015-01-01

    Growing evidence suggests how global background levels of atmospheric carbon dioxide (CO2) are increasing and this impacts environmental quality and human and ecological health. Data from less developed countries are sparse. We determined spatial and temporal variations in concentrations of CO2 in selected locations in Ibadan, Nigeria with identifiable prominent outdoor sources. Activity driven areas in north and south-west areas were identified and marked with a global positioning system. Waste management practices and activities generating CO2 were documented and described using a technician observation checklist. CO2 levels were measured using a portable TELAIRE 7001 attached to HOBO U12 data loggers across seasons. Mean CO2 levels were compared over seasons, i.e. rainy season months and the dry season months. While CO2 levels recorded outdoors in study areas were comparable to available international data, routine monitoring is recommended to further characterize concurrent pollutants in fossil fuel combustion emissions with known deleterious health effects.

  7. Spatial variation in the structure of fish assemblages in the Vaalbos National Park, South Africa

    Directory of Open Access Journals (Sweden)

    I.A. Russell

    1997-01-01

    Full Text Available Fish assemblages were sampled at nine sites in the lower Vaal River in the Vaalbos National Park and adjacent properties. A total of 1543 fish from 10 species was recorded. Ordination revealed spatial variation in assemblage structure, with the distinction primarily between communities in rapids and deep pools. Flow velocity, depth and percentage cover were important determinants offish assemblage structure. The length frequency distribution of abundant species indicated successful recruitment. Several differences in the species compliment compared to earlier studies were evident, including high abundance of Barbus paludinosus and Austro^lanis sclateri, and the absence of Barbus anoplus. The length-mass relationships of large cyprmids indicated long-term declines in the physical condition of fish.

  8. The Spatial Variation of LURR and Seismic Tendency in Western United States

    Institute of Scientific and Technical Information of China (English)

    Zhang Huihui; Yin Xiangchu; Liang Naigang

    2005-01-01

    Load-Unload Response Ratio (LURR) is a new promising approach to earthquake prediction.In the previous years, a series of successful medium-term predictions have been made for strong earthquakes on the Chinese mainland using this method. In order to investigate whether the LURR method applies to different tectonic regimes, i.e., whether it is universal, the San Andreas Fault and its vicinities are chosen as the study region in this paper. The spatial variation of LURR in the western United States (30°~ 50°N, 100°~ 130°W) is studied in detail and the earthquake tendency in this region is discussed based on historic earthquake cases.

  9. Detection of spatial variations in temporal trends with a quadratic function.

    Science.gov (United States)

    Moraga, Paula; Kulldorff, Martin

    2016-08-01

    Methods for the assessment of spatial variations in temporal trends (SVTT) are important tools for disease surveillance, which can help governments to formulate programs to prevent diseases, and measure the progress, impact, and efficacy of preventive efforts already in operation. The linear SVTT method is designed to detect areas with unusual different disease linear trends. In some situations, however, its estimation trend procedure can lead to wrong conclusions. In this article, the quadratic SVTT method is proposed as alternative of the linear SVTT method. The quadratic method provides better estimates of the real trends, and increases the power of detection in situations where the linear SVTT method fails. A performance comparison between the linear and quadratic methods is provided to help illustrate their respective properties. The quadratic method is applied to detect unusual different cervical cancer trends in white women in the United States, over the period 1969 to 1995. © The Author(s) 2013.

  10. Spatial and temporal variations of mercury levels in Okefenokee invertebrates: southeast Georgia.

    Science.gov (United States)

    George, Bagie M; Batzer, Darold

    2008-03-01

    Accumulation of mercury in wetland ecosystems has raised concerns about impacts on wetland food webs. This study measured concentrations of mercury in invertebrates of the Okefenokee Swamp in Georgia, focusing on levels in amphipods, odonates, and crayfish. We collected and analyzed total mercury levels in these invertebrates from 32 sampling stations across commonly occurring sub-habitats. Sampling was conducted in December, May, and August over a two-year period. The highest levels of mercury were detected in amphipods, with total mercury levels often in excess of 20 ppm. Bioaccumulation pathways of mercury in invertebrates of the Okefenokee are probably complex; despite being larger and higher in the food chain, levels in odonates and crayfish were much lower than in amphipods. Mercury levels in invertebrates varied temporally with the highest levels detected in May. There was a lack of spatial variation in mercury levels which is consistent with aerial deposition of mercury.

  11. Spatial variation in Earth structure inferred by GNSS seasonal deformations due to snow loads in northeast Japan

    Science.gov (United States)

    Hirose, H.; Kurisu, R.; Nishimura, T.

    2016-12-01

    Seasonal variations are observed in GNSS site coordinate time series (e.g., Murakami and Miyazaki, 2001; Munekane et al., 2004). Heki (2001) showed that snow loads cause seasonal subsidence in winter in the Tohoku region, northeast Japan from the Geospatial Information Authority of Japan's GEONET GNSS daily site coordinates during the period 1999.0-2001.0. It becomes worth reevaluating this issue because the observed GNSS data are accumulated over 10 years and the amplitude of apparent seasonal components can be reduced with revised analysis strategies (e.g., Nakagawa et al., 2009). Here we show that the correlation between a seasonal variation in GNSS vertical displacement time-series and snow depth measured by Japan Meteorological Agency's AMeDAS over 10 years is good in some areas with the largest snow depths among the study areas, the ratio of seasonal subsidence to snow depth shows spatial variation, and the variation can be explained by spatial variation of underground structure.

  12. Modeling fixation locations using spatial point processes.

    Science.gov (United States)

    Barthelmé, Simon; Trukenbrod, Hans; Engbert, Ralf; Wichmann, Felix

    2013-10-01

    Whenever eye movements are measured, a central part of the analysis has to do with where subjects fixate and why they fixated where they fixated. To a first approximation, a set of fixations can be viewed as a set of points in space; this implies that fixations are spatial data and that the analysis of fixation locations can be beneficially thought of as a spatial statistics problem. We argue that thinking of fixation locations as arising from point processes is a very fruitful framework for eye-movement data, helping turn qualitative questions into quantitative ones. We provide a tutorial introduction to some of the main ideas of the field of spatial statistics, focusing especially on spatial Poisson processes. We show how point processes help relate image properties to fixation locations. In particular we show how point processes naturally express the idea that image features' predictability for fixations may vary from one image to another. We review other methods of analysis used in the literature, show how they relate to point process theory, and argue that thinking in terms of point processes substantially extends the range of analyses that can be performed and clarify their interpretation.

  13. Impacts of climatic and marine environmental variations on the spatial distribution of Ommastrephes bartramii in the Northwest Pacific Ocean

    Institute of Scientific and Technical Information of China (English)

    YU Wei; CHEN Xinjun; YI Qian; GAO Guoping; CHEN Yong

    2016-01-01

    Ommastrephes bartramii is an ecologically dependent species and has great commercial values among the Asia-Pacific countries. This squid widely inhabits the North Pacific, one of the most dynamic marine environments in the world, subjecting to multi-scale climatic events such as the Pacific Decadal Oscillation (PDO). Commercial fishery data from the Chinese squid-jigging fleets during 1995-2011 are used to evaluate the influences of climatic and oceanic environmental variations on the spatial distribution of O. bartramii. Significant interannual and seasonal variability are observed in the longitudinal and latitudinal gravity centers (LONG and LATG) of fishing ground of O. bartramii. The LATG mainly occurred in the waters with the suitable ranges of environmental variables estimated by the generalized additive model. The apparent north-south spatial shift in the annual LATG appeares to be associated with the PDO phenomenon and is closely related to the sea surface temperature (SST) and sea surface height (SSH) on the fishing ground, whereas the mixed layer depth (MLD) might contribute limited impacts to the distribution pattern of O. bartramii. The warm PDO regimes tend to yield cold SST and low SSH, resulting in a southward shift of LATG, while the cold PDO phases provid warm SST and elevated SSH, resulting in a northward shift of LATG. A regression model is developed to help understand and predict the fishing ground distributions of O. bartramii and improve the fishery management.

  14. Temporal and spatial variations of soil carbon dioxide, methane, and nitrous oxide fluxes in a Southeast Asian tropical rainforest

    Directory of Open Access Journals (Sweden)

    M. Itoh

    2010-09-01

    Full Text Available To clarify the factors controlling temporal and spatial variations of soil carbon dioxide (CO2, methane (CH4, and nitrous oxide (N2O fluxes, we investigated these gas fluxes and environmental factors in a tropical rainforest in Peninsular Malaysia. Temporal variation of CO2 flux in a 2-ha plot was positively related to soil water condition and rainfall history. Spatially, CO2 flux was negatively related to soil water condition. When CO2 flux hotspots were included, no other environmental factors such as soil C or N concentrations showed any significant correlation. Although the larger area sampled in the present study complicates explanations of spatial variation of CO2 flux, our results support a previously reported bipolar relationship between the temporal and spatial patterns of CO2 flux and soil water condition observed at the study site in a smaller study plot. Flux of CH4 was usually negative with little variation, resulting in the soil at our study site functioning as a CH4 sink. Both temporal and spatial variations of CH4 flux were positively related to the soil water condition. Soil N concentration was also related to the spatial distribution of CH4 flux. Some hotspots were observed, probably due to CH4 production by termites, and these hotspots obscured the relationship between both temporal and spatial variations of CH4 flux and environmental factors. Temporal variation of N2O flux and soil N2O concentration was large and significantly related to the soil water condition, or in a strict sense, to rainfall history. Thus, the rainfall pattern controlled wet season N2O production in soil and its soil surface flux. Spatially, large N2O emissions were detected in wet periods at wetter and anaerobic locations, and were thus determined by soil

  15. Are spatial variations in the diets of hydrothermal fauna linked to local environmental conditions?

    Science.gov (United States)

    De Busserolles, F.; Sarrazin, J.; Gauthier, O.; Gélinas, Y.; Fabri, M. C.; Sarradin, P. M.; Desbruyères, D.

    2009-09-01

    Trophic relationships in Bathymodiolus azoricus mussel bed communities on the Tour Eiffel hydrothermal edifice (Lucky Strike) were assessed using δ 13C and δ 15N signatures from 14 hydrothermal species. The nutritional basis of B. azoricus was also investigated with δ 34S. Faunal samples and environmental data (temperature, pH, total dissolved sulfide, iron and copper concentrations) were collected from 12 different locations on the edifice. Chemical conditions varied between microhabitats, and were all correlated to temperature. Carbon and nitrogen isotopic results revealed the presence of two, apparently independent, trophic groups. The first was composed of symbiont-bearing fauna ( B. azoricus and their associated polychaetes Branchipolynoe seepensis), while the second enclosed heterotrophic fauna (bacterivores, detritivores, scavengers, predators). A majority of mussels displayed δ 13C values ranging from -27‰ to -34‰, supporting thiotrophy as the dominant nutritional pathway at Tour Eiffel, with methanotrophy and filter feeding emerging as secondary strategies. This result was corroborated by δ 34S signatures. However, higher δ 13C values in larger mussels suggested that, as they grow, B. azoricus mussels rely more heavily on their methanotrophic endosymbionts. Significant spatial variability in isotopic signatures for single faunal species was observed at the scale of the edifice for three species ( B. azoricus, B. seepensis, Amathys lutzi), and environmental conditions explained variation in isotopic signatures for one-third of the species. This confirms the hypothesis raised by several authors on the role of hydrothermal fluids on the trophic network at small spatial scales. We suggest that vent fluid characteristics, by influencing microbial production, are key factors in the variation of local carbon sources at vents.

  16. Assessments of potential spatial-temporal variations in phosphorus distribution and fractionation in river bed sediments

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingyu [Department of Environmental Geographic and Geological Sciences, Lehman College of the City University of New York, New York (United States); Graduate Center, Ph.D. Program in Earth and Environmental Sciences, City University of New York, New York (United States); Pant, Hari K. [Department of Environmental Geographic and Geological Sciences, Lehman College of the City University of New York, New York (United States)

    2011-02-15

    Sediment characteristics influence the distribution and bioavailability of phosphorus (P) in river sediments. In this study, we analyzed different P fractions in the sediments of the Bronx River, New York City, NY, using sequential extraction. The results showed that the average P pool rank order was HCl-P > NaOH-P > NaHCO{sub 3}-P > residue-P, and their relative proportions were 3.7: 2.0: 1.4: 1 in sediments collected in 2006, while HCl-P > NaOH-P > residue-P > NaHCO{sub 3}-P, with their relative proportions of 27.8:6.2:2.7:1 in the sediments obtained in 2007. The strong correlation between microbial P and organic P (OP), along with the changes in microbial P over time indicate that most of the OP in the river bed sediments is potentially bioavailable. The sediment transport, deposition, assimilation, the exchange of P between sediments and water columns, the land use changes, raw sewer discharge, gas spill, construction, fertilizer application, etc., as well as the hydro-climatic changes could result in the spatial and temporal variations in P bioavailability in the river bed sediments. The estimations of P pools and their bioavailability in river bed sediments could help determine the spatial and temporal variations in P transport and impacts of land use on water quality, in turn, help regulate P in the river's watershed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Estimating the Impact of Urbanization on Air Quality in China Using Spatial Regression Models

    Directory of Open Access Journals (Sweden)

    Chuanglin Fang

    2015-11-01

    Full Text Available Urban air pollution is one of the most visible environmental problems to have accompanied China’s rapid urbanization. Based on emission inventory data from 2014, gathered from 289 cities, we used Global and Local Moran’s I to measure the spatial autorrelation of Air Quality Index (AQI values at the city level, and employed Ordinary Least Squares (OLS, Spatial Lag Model (SAR, and Geographically Weighted Regression (GWR to quantitatively estimate the comprehensive impact and spatial variations of China’s urbanization process on air quality. The results show that a significant spatial dependence and heterogeneity existed in AQI values. Regression models revealed urbanization has played an important negative role in determining air quality in Chinese cities. The population, urbanization rate, automobile density, and the proportion of secondary industry were all found to have had a significant influence over air quality. Per capita Gross Domestic Product (GDP and the scale of urban land use, however, failed the significance test at 10% level. The GWR model performed better than global models and the results of GWR modeling show that the relationship between urbanization and air quality was not constant in space. Further, the local parameter estimates suggest significant spatial variation in the impacts of various urbanization factors on air quality.

  18. Modelling spatial patterns of economic activity in the Netherlands

    CERN Document Server

    Yang, Jung-Hun; Frenken, Koen; Van Oort, Frank; Visser, Evert-Jan

    2012-01-01

    Understanding how spatial configurations of economic activity emerge is important when formulating spatial planning and economic policy. Not only micro-simulation and agent-based model such as UrbanSim, ILUMAS and SIMFIRMS, but also Simon's model of hierarchical concentration have widely applied, for this purpose. These models, however, have limitations with respect to simulating structural changes in spatial economic systems and the impact of proximity. The present paper proposes a model of firm development that is based on behavioural rules such as growth, closure, spin-off and relocation. An important aspect of the model is that locational preferences of firms are based on agglomeration advantages, accessibility of markets and congestion, allowing for a proper description of concentration and deconcentration tendencies. By comparing the outcomes of the proposed model with real world data, we will calibrate the parameters and assess how well the model predicts existing spatial configurations and decide. The...

  19. Spatial variations of sea-level rise and impacts: an application of DIVA

    OpenAIRE

    Brown, S; Nicholls, R.J.; Lowe, J A; Hinkel, J.

    2013-01-01

    Due to complexities of creating sea-level rise scenarios, impacts of climate-induced sea-level rise are often produced from a limited number of models assuming a global uniform rise in sea level. A greater number of models, including those with a pattern reflecting regional variations would help to assure reliability and a range of projections, indicating where models agree and disagree. This paper determines how nine new patterned-scaled sea-level rise scenarios (plus the uniform and pattern...

  20. A spatial and nonstationary model for the frequency of extreme rainfall events

    DEFF Research Database (Denmark)

    Gregersen, Ida Bülow; Madsen, Henrik; Rosbjerg, Dan;

    2013-01-01

    Changes in the properties of extreme rainfall events have been observed worldwide. In relation to the discussion of ongoing climatic changes, it is of high importance to attribute these changes to known sources of climate variability. Focusing on spatial and temporal changes in the frequency...... of extreme rainfall events, a statistical model is tested for this purpose. The model is built on the theory of generalized linear models and uses Poisson regression solved by generalized estimation equations. Spatial and temporal explanatory variables can be included simultaneously, and their relative...... importance can be assessed. Additionally, the model allows for a spatial correlation between the measurements. Data from a Danish rain gauge network are used as a case study for model evaluation. Focusing on 10 min and 24 h rainfall extremes, it was found that regional variation in the mean annual...

  1. Spatial emission modelling for residential wood combustion in Denmark

    DEFF Research Database (Denmark)

    Plejdrup, Marlene Schmidt; Nielsen, Ole-Kenneth; Brandt, Jørgen

    2016-01-01

    Residential wood combustion (RWC) is a major contributor to atmospheric pollution especially for particulate matter. Air pollution has significant impact on human health, and it is therefore important to know the human exposure. For this purpose, it is necessary with a detailed high resolution...... spatial distribution of emissions. In previous studies as well as in the model previously used in Denmark, the spatial resolution is limited, e.g. municipality or county level. Further, in many cases models are mainly relying on population density data as the spatial proxy for distributing the emissions....... This paper describes the new Danish model for high resolution spatial distribution of emissions from RWC to air. The new spatial emission model is based on information regarding building type, and primary and supplementary heating installations from the Danish Building and Dwelling Register (BBR), which...

  2. Winter wheat growth spatial variation monitoring through hyperspectral remote sensing image

    Science.gov (United States)

    Song, Xiaoyu; Li, Ting; Wang, Jihua; Gu, Xiaohe; Xu, Xingang

    2015-10-01

    This work aims at quantifying the winter wheat growth spatial heterogeneity captured by hyperspectral airborne images. The field experiment was conducted in 2001 and 2002 and airborne hyperspectral remote-sensing data was acquired at noon on 11 April 2001 using an operational modular imaging spectrometer (OMIS). Totally 12 winter fields which covered by both dense and sparse winter wheat canopies were selected to analysis the winter wheat growth heterogeneity. The experimental semi-variograms for bands covered from invisible to mid-infrared were computed for each field then the theoretical models were be fitted with least squares algorithm for spherical model, exponential model. The optimization model was selected after evaluated by R-square. Three key terms in each model, the sill, the range, and nugget variance were then calculated from the models. The study results show that the sill, range and nugget for same field wheat were varied with the wavelength from blue to mid infrared bands. Although wheat growth in different fields showed different spatial heterogeneity, they all showed an obvious sill pattern. The minimum of mean range value was 7.52 m for mid-infrared bands while the maximum value was 91.71 m for visible bands. The minimum of mean sill value ranged from 1.46 for visible bands to 39.76 for NIR bands, the minimum of mean nugget value ranged from 0.06 for visible bands to5.45 for mid-infrared bands. This study indicate that remote sensing image is important for crop growth spatial heterogeneity study. But it is necessary to explore the effect of different wavelength of image data on crop growth semi-variogram estimation and find out which band data could be used to estimate crop semi-variogram reliably.

  3. Free-streaming radiation in cosmological models with spatial curvature

    Science.gov (United States)

    Wilson, M. L.

    1982-01-01

    The effects of spatial curvature on radiation anisotropy are examined for the standard Friedmann-Robertson-Walker model universes. The effect of curvature is found to be very important when considering fluctuations with wavelengths comparable to the horizon. It is concluded that the behavior of radiation fluctuations in models with spatial curvature is quite different from that in spatially flat models, and that models with negative curvature are most strikingly different. It is therefore necessary to take the curvature into account in careful studies of the anisotropy of the microwave background.

  4. Recent Research toward Understanding Spatial, Temporal, and Climatic Variation in Stream Temperatures across the Northwest U.S.

    Science.gov (United States)

    Isaak, D.; Roper, B.; Luce, C.; Holden, Z.

    2012-12-01

    Global air temperature increases raise concerns about effects on thermal regimes of the Earth's rivers and streams. These concerns are acute in the Northwest U.S. due to legislatively mandated water quality standards and the importance of recreational and commercial fisheries for cold-water species such as salmon and trout. Efforts to study climate effects on stream thermal regimes are limited by sparse long-term monitoring records, resulting in a lack of information on historical spatial and temporal variation from which to measure departure. We present research from the last five years that begins to address these shortcomings, including: 1) estimation of stream warming rates in recent decades associated with long-term climate change (+0.11 °C/decade for mean annual temperatures; +0.22 °C/decade for summer temperatures), 2) development of an inexpensive protocol for monitoring full-year temperatures in dynamic mountain streams, 3) rapid expansion of an informal regional monitoring network from 3,000 sites in the last three years, 4) development and use of high-resolution (i.e., 100's of meters) air temperature microclimate models to understand variation in stream temperatures, 5) development of NorWeST, a comprehensive stream temperature database consisting of > 45,000 summers of temperature measurement at > 15,000 unique stream sites, and 6) use of new spatial statistical stream network models with NorWeST to krige predictions at unsampled locations and develop thermal information for most of the region's 350,000 stream kilometers. There is much yet to be learned regarding thermal regimes in rivers and streams but the accelerating pace of knowledge discovery driven by inexpensive sensors, computational improvements, geospatial technologies, and new analyses suggests that many important remaining unknowns will be resolved in the next five years.

  5. The Spatial Variation of the Cooling Lines in the Reflection Nebula NGC7023

    CERN Document Server

    Bernard-Salas, J; Köhler, M; Abergel, A; Arab, H; Lebouteiller, V; Pinto, C; van der Wiel, M H D; White, G J; Hoffmann, M

    2015-01-01

    Context: The north-west photo-dissociation region (PDR) in the reflection nebula NGC 7023 displays a complex structure. Filament-like condensations at the edge of the cloud can be traced via the emission of the main cooling lines, offering a great opportunity to study the link between the morphology and energetics of these regions. Aims: We study the spatial variation of the far-infrared fine-structure lines of [C II] (158 um) and [O I] (63 and 145 um). These lines trace the local gas conditions across the PDR. Methods: We used observations from the Herschel/PACS instrument to map the spatial distribution of these fine-structure lines. The observed region covers a square area of about 110" x 110" with an angular resolution that varies from 4" to 11". We compared this emission with ground-based and Spitzer observations of H2 lines, Herschel/SPIRE observations of CO lines, and Spitzer/IRAC 3.6 um images that trace the emission of polycyclic aromatic hydrocarbons. Results: The [C II] (158 um) and [O I] (63 and 1...

  6. Spatial variation of physicochemical and bacteriological parameters elucidation with GIS in Rangat Bay, Middle Andaman, India

    Science.gov (United States)

    Dheenan, P. S.; Jha, Dilip Kumar; Vinithkumar, N. V.; Ponmalar, A. Angelin; Venkateshwaran, P.; Kirubagaran, R.

    2014-01-01

    The purpose of this study was to determine the concentration, distribution of bacteria and physicochemical property of surface seawater in Rangat Bay, Middle Andaman, Andaman Islands (India). The bay experiences tidal variations. Perhaps physicochemical properties of seawater in Rangat Bay were found not to vary significantly. The concentration of faecal streptococci was high (2.2 × 103 CFU/100 mL) at creek and harbour area, whereas total coliforms were high (7.0 × 102 CFU/100 mL) at mangrove area. Similarly, total heterotrophic bacterial concentration was high (5.92 × 104 CFU/100 mL) in mangrove and harbour area. The Vibrio cholerae and Vibrio parahaemolyticus concentration was high (4.2 × 104 CFU/100 mL and 9 × 103 CFU/100 mL) at open sea. Cluster analysis showed grouping of stations in different tidal periods. The spatial maps clearly depicted the bacterial concentration pattern in the bay. The combined approach of multivariate analysis and spatial mapping techniques was proved to be useful in the current study.

  7. Variation in spatial scale of competing polydomous twig-nesting ants in coffee agroecosystems.

    Science.gov (United States)

    Mathis, Kaitlyn A; Philpott, Stacy M; Ramirez, Santiago R

    2016-08-01

    Arboreal ants are both highly diverse and ecologically dominant in the tropics. This ecologically important group is particularly useful in ongoing efforts to understand processes that regulate species diversity and coexistence. Our study addresses how polydomy can influence patterns of nest occupation in competing arboreal ants. We examined the spatial structure of nest occupation (nest distance, abundance and density) in three polydomous co-occurring twig-nesting ant species (Pseudomyrmex simplex, P. ejectus and P. PSW-53) by mapping twigs occupied by ants from each species within plots in our study site. We then used two colony structure estimators (intraspecific aggression and cuticular hydrocarbon variation) to determine the relative degree of polydomy for each species. All work was conducted in coffee agroforests in Chiapas, Mexico. Our results revealed that the two species with highest abundance and nest density were also highly polydomous, where both species had either single or multiple non-aggressive colonies occupying nests on a large spatial scale (greater than the hectare level). Our results also indicate that the species with the lowest abundance and density is less polydomous, occupying several overlapping and territorial colonies at the hectare level in which multiple colonies never co-occur on the same host plant. These results contribute evidence that successful coexistence and highly polydomous colony structure may allow ants, through reduced intraspecific aggression, to successfully occupy more nests more densely than ant species that have multiple territorial colonies. Furthermore our study highlights the importance of considering intraspecific interactions when examining community assembly of ants.

  8. Diatoms on the carapace of common snapping turtles: Luticola spp. dominate despite spatial variation in assemblages

    Science.gov (United States)

    Wu, Shelly C.; Bergey, Elizabeth A.

    2017-01-01

    Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina) across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.). Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups–the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas) than on northern turtles (where mean abundance/state was > 10%). L. cf. mutica was the most abundant species (40%) on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts. PMID:28192469

  9. Spatial variations of PAH properties in M17SW revealed by Spitzer/IRS spectral mapping

    CERN Document Server

    Yamagishi, M; Ishihara, D; Oyabu, S; Suzuki, T; Onaka, T; Nagayama, T; Umemoto, T; Minamidani, T; Nishimura, A; Matsuo, M; Fujita, S; Tsuda, Y; Kohno, M; Ohashi, S

    2016-01-01

    We present $Spitzer$/IRS mid-infrared spectral maps of the Galactic star-forming region M17 as well as IRSF/SIRIUS Br$\\gamma$ and Nobeyama 45-m/FOREST $^{13}$CO ($J$=1--0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2 $\\mu$m. We find that the PAH emission features are bright in the region between the HII region traced by Br$\\gamma$ and the molecular cloud traced by $^{13}$CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially-resolved maps, we examine spatial variations of the PAH properties in detail. As a result, we find that the interband ratio of PAH 7.7 $\\mu$m/PAH 11.3 $\\mu$m varies locally near M17SW, but rather independently of the distance from the OB stars in M17, suggesting that the ionization degree of PAHs is mainly controlled by local conditions rather than the global UV environments determined by the OB stars in M17. We also find tha...

  10. Investigation of outdoor BTEX: Concentration, variations, sources, spatial distribution, and risk assessment.

    Science.gov (United States)

    Miri, Mohammad; Rostami Aghdam Shendi, Maryam; Ghaffari, Hamid Reza; Ebrahimi Aval, Hamideh; Ahmadi, Ehsan; Taban, Ebrahim; Gholizadeh, Abdolmajid; Yazdani Aval, Mohsen; Mohammadi, Amir; Azari, Ali

    2016-11-01

    The aim of this study was to measure BTEX (benzene, toluene, ethylbenzene, and xylenes) concentrations in the ambient air of Tehran, the capital of Iran, and investigate their seasonal variations, probable sources, spatial mapping, and risk assessment. The concentrations of BTEX were measured using a continuous monitoring device installed in seven stations around the city. Spatial mapping procedure was conducted using the inverse distance weighting (IDW) method. Monte Carlo simulation was used to assess the carcinogenic and noncarcinogenic risks imposed by BTEX. The highest and lowest annual mean concentrations of toluene and ethylbenzene were recorded as 16.25 and 3.63 μg m(-3), respectively. The maximum (6.434) and minimum (3.209) toluene/benzene (T/B) ratio was observed in summer and winter, respectively. The spatial distribution of BTEX pollution indicated that the highest concentrations were found along the major roads because of heavy traffic. Spearman's rank correlation coefficients and concentration ratios showed that BTEX were produced by the multiemission sources. The mean of inhalation lifetime cancer risk (LTCR) for benzene was 3.93 × 10(-7), which is lower than the limits recommended by the United States Environmental Protection Agency (US EPA) and the World Health Organization (WHO). The hazard quotient (HQ), noncarcinogenic risk index, for all BTEX compounds was <1. The obtained results showed no threat of BTEX concentrations to human health. However, as the concentrations of BTEX will increase due to the rapid growth of vehicles and industrial activities, much effort is required to control and manage the levels of these compounds in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Spatial Variation and Resuscitation Process Affecting Survival after Out-of-Hospital Cardiac Arrests (OHCA.

    Directory of Open Access Journals (Sweden)

    Chien-Chou Chen

    Full Text Available Ambulance response times and resuscitation efforts are critical predictors of the survival rate after out-of-hospital cardiac arrests (OHCA. On the other hand, rural-urban differences in the OHCA survival rates are an important public health issue.We retrospectively reviewed the January 2011-December 2013 OHCA registry data of Kaohsiung City, Taiwan. With particular focus on geospatial variables, we aimed to unveil risk factors predicting the overall OHCA survival until hospital admission. Spatial analysis, network analysis, and the Kriging method by using geographic information systems were applied to analyze spatial variations and calculate the transport distance. Logistic regression was used to identify the risk factors for OHCA survival.Among the 4,957 patients, the overall OHCA survival to hospital admission was 16.5%. In the multivariate analysis, female sex (adjusted odds ratio:, AOR, 1.24 [1.06-1.45], events in public areas (AOR: 1.30 [1.05-1.61], exposure to automated external defibrillator (AED shock (AOR: 1.70 [1.30-2.23], use of laryngeal mask airway (LMA (AOR: 1.35 [1.16-1.58], non-trauma patients (AOR: 1.41 [1.04-1.90], ambulance bypassed the closest hospital (AOR: 1.28 [1.07-1.53], and OHCA within the high population density areas (AOR: 1.89 [1.55-2.32] were positively associated with improved OHCA survival. By contrast, a prolonged total emergency medical services (EMS time interval was negatively associated with OHCA survival (AOR: 0.98 [0.96-0.99].Resuscitative efforts, such as AED or LMA use, and a short total EMS time interval improved OHCA outcomes in emergency departments. The spatial heterogeneity of emergency medical resources between rural and urban areas might affect survival rate.

  12. Spatial and temporal variations of gas geochemistry at Mt. Ontake, Japan

    Science.gov (United States)

    Kagoshima, Takanori; Sano, Yuji; Takahata, Naoto; Ishida, Akizumi; Tomonaga, Yama; Roulleau, Emilie; Pinti, Daniele L.; Fischer, Tobias P.; Lan, Tefang; Nishio, Yoshiro; Tsunogai, Urumu; Guo, Zhengfu

    2016-10-01

    This report describes spatial and temporal variations of helium, carbon, and nitrogen isotopes measured in CO2-rich bubbling gases from natural springs associated with Mt. Ontake (central Honshu, Japan) from November 1981 through September 2015. During the entire period, the 3He/4He ratio decreased concomitantly with increasing distance of the sampling site from the central cone. In contrast, the CO2/3He ratios and the δ13C values of CO2 increased with distance. These spatial trends became more pronounced after the September 27, 2014 Ontake eruption, suggesting reactivation of the volcano plumbing system with enhanced emission of magmatic volatiles, although the spatial trend of nitrogen isotopes disappeared. The 3He/4He ratios of the most proximal site to the central cone remained constant until 2000, apparently increasing from June 2003 through October 2014. They became constant soon after the eruption until September 2015. The ten-year 3He enhancement might have been a precursor of the 2014 Ontake eruption. In contrast, δ13C values of CO2 at the same site remained constant through this period. The lack of δ13C anomaly might be attributable to 1) negligibly small amounts of magmatic CO2 introduced into the source of hot springs compared to ambient CO2 in the air-saturated aquifer, or 2) close resemblance of the carbon signature of magmatic CO2 to that of ambient CO2. Therefore its addition cannot change the overall δ13C value of the sampled hot springs. At distal sampling sites, no measurable change of helium, carbon, or nitrogen isotopes was observed in relation to the 2014 Ontake eruption, suggesting that the effect of this eruption on the Ontake hydrothermal system was geographically localized.

  13. Spatial Variations of the Extinction Law in the Galactic Disk from Infrared Observations

    CERN Document Server

    Gontcharov, George

    2016-01-01

    Infrared photometry in the J (1.2 microns), H (1.7 microns), Ks (2.2 microns) bands from the 2MASS catalogue and in the W1 (3.4 microns), W2 (4.6 microns), W3 (12 microns), W4 (22 microns) bands from the WISE catalogue is used to reveal the spatial variations of the interstellar extinction law in the infrared near the midplane of the Galaxy by the method of extrapolation of the extinction law applied to clump giants. The variations of the coefficients E(H-W1)/E(H-Ks), E(H-W2)/E(H-Ks), E(H-W3)/E(H-Ks), and E(H-W4)/E(H-Ks) along the line of sight in 2 deg per 2 deg squares of the sky centered at b=0 and l=20, 30, ..., 330, 340 deg as well as in several 4 deg per 4 deg squares with |b|=10 are considered. The results obtained here agree with those obtained by Zasowski et al. in 2009 using 2MASS and Spitzer-IRAC photometry for the same longitudes and similar photometric bands, confirming their main result: in the inner (relative to the Sun) Galactic disk, the fraction of fine dust increases with Galactocentric dis...

  14. Spatial and seasonal variations of the contamination within water body of the Grand Canal, China

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiaolong, E-mail: wangxl@niglas.ac.c [State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (China); Han Jingyi [Environmental Policy Group, Department of Social Sciences, Wageningen University, Hollandseweg 1, 6706 KN Wageningen (Netherlands); Xu Ligang; Zhang Qi [State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (China)

    2010-05-15

    To delineate the character of contaminations in the Grand Canal, China, a three-year study (2004-2006) was conducted to investigate variations the water quality in the canal. Results showed that the variation of water quality within the Grand Canal was of there is remarkable spatial and seasonal heterogeneity regarding water quality within the Canal. Values of contaminants in dry-season were obviously higher than those in wet-season. Sites influenced strongly by industry and urbanization showed higher contents of nutrients and lower levels of dissolved oxygen in water body; moreover these sites were severely polluted by dissolved metals with the contents of cadmium, chromium and copper exceeding the Criteria Maximum Concentration (CMC), US EPA. Multivariate statistical analysis suggested nutrient and dissolved metals pollution was the dominant environmental problems within the Canal. Anthropogenic influences played a dominant role in the character of contaminations in the Grand Canal. - The Grand Canal has been severely polluted by dissolved metals and nutrient due to anthropogenic activities

  15. Bacterial diversity, composition and temporal-spatial variation in the sediment of Jiaozhou Bay, China

    Institute of Scientific and Technical Information of China (English)

    LIU Xin; XIAO Tian; LUAN Qingshan; ZHANG Wenyan; WANG Mengqiang; YUE Haidong

    2011-01-01

    Studies on the diversity and distribution of bacterial populations will improve the overall understanding of the global patterns of marine bacteria and help to comprehend local biochemical processes and environments. We evaluated the composition and the dynamics of bacterial communities in the sediment of Jiaozhou Bay (China) using PCR-denaturing gradient gel electrophoresis (DGGE). Sediment samples were collected from 10 different sites in May, August, and November 2008 and in February 2009.There was significant temporal variation in bacterial community composition at all sites. However, the spatial variation was very small. The DGGE analyses of bacterial communities were used to divide the 10 stations into three types. Canonical correspondence analysis (CCA) revealed that the changes in bacterial communities were driven by sediment properties. Sequence analysis of DGGE band-derived 16S rRNA gene fragments revealed that the dominant bacterial groups in the sediment were of the classes γ-proteobacteria and δ-proteobacteria and phyla Bacteroidetes and Nitrospirae. Our results provide considerable insight into the bacterial community structure in Jiaozhou Bay, China.

  16. Temporal and spatial variation of rocky shores intertidal benthic communities in Southeast Brazil

    Directory of Open Access Journals (Sweden)

    Gabriela C. Zamprogno

    2012-12-01

    Full Text Available The relationships between environmental factors and temporal and spatial variations of benthic communities of three rocky shores of the state of Espírito Santo, Southeast Brazil, were studied. Sampling was conducted every three months, from August 2006 to May 2007, using intersection points. Chthamalus bisinuatus (Pilsbry, 1916 (Crustacea and Brachidontes spp. (Mollusca were the most abundant taxa, occupying the upper level of the intertidal zone of the rocky shore. The species richness was higher at the lower levels. The invasive species Isognomon bicolor (C. B. Adams, 1845 (Mollusca occurred at low densities in the studied areas. The clustering analysis dendrogram indicated a separation of communities based on exposed and sheltered areas. According to the variance analyses, the communities were significantly different among the studied areas and seasons. The extent of wave exposure and shore slope influenced the species variability. The Setibão site showed the highest diversity and richness, most likely due to greater wave exposure. The communities showed greater variation in the lower levels where environmental conditions were less severe, relative to the other levels.

  17. Long-term Spatial and Temporal Variations of Aurora Borealis Events in the Period 1700 - 1905

    Science.gov (United States)

    Vázquez, M.; Vaquero, J. M.; Gallego, M. C.

    2014-05-01

    Catalogues and other records of aurora-borealis events were used to study the long-term spatial and temporal variation of these phenomena in the period from 1700 to 1905 in the Northern Hemisphere. For this purpose, geographic and geomagnetic coordinates were assigned to approximately 27 000 auroral events with more than 80 000 observations. They were analyzed separately in three large-scale areas: i) Europe and North Africa, ii) North America, and iii) Asia. There was a clear need to fill some gaps existing in the records so as to have a reliable proxy of solar activity, especially during the 18th century. In order to enhance the long-term variability, an 11-year smoothing window was applied to the data. Variations in the cumulative numbers of auroral events with latitude (in both geographic and geomagnetic coordinates) were used to discriminate between the two main solar sources: coronal mass ejections and high-speed streams from coronal holes. The characteristics of the associated auroras correlate differently with the solar-activity cycle.

  18. SHTV, as a technique for core calculation using spatial homogenization and temperature variation

    Energy Technology Data Exchange (ETDEWEB)

    Moghaddam, Nader Maleki, E-mail: nader.moghaddam@gmail.co [Department of Nuclear Engineering and Physics, Amir Kabir University of Technology (Tehran polytechnique), Hafez Street, Tehran (Iran, Islamic Republic of); Zahedinejad, Ehsan, E-mail: ehsanzahedinejad@gmail.co [Department of Energy Engineering, Sharif University of Technology, Azadi Street, Tehran (Iran, Islamic Republic of); Kashi, Samira, E-mail: smr.kashi@gmail.co [Department of Nuclear Engineering, Shahid Beheshti University, Evin Street, Tehran (Iran, Islamic Republic of); Davilu, Hadi, E-mail: Davilu@aut.ac.i [Department of Nuclear Engineering and Physics, Amir Kabir University of Technology (Tehran polytechnique), Hafez Street, Tehran (Iran, Islamic Republic of)

    2010-09-15

    The accuracy of static neutronic parameters in the nuclear reactors depends upon the determination of group constants of the diffusion equation in the desired geometry. Although several methods have been proposed for calculating these parameters, there is still the need for more reliable methods. In this paper a powerful and innovative method based on Spatial Homogenization and Temperature Variation (SHTV) of physical properties of a WWER-1000 nuclear reactor core for calculating the relative power distribution of Fuel Assemblies (FA) and the hot fuel rod, is presented. The method is based on replacing the heterogeneous lattices of materials with different properties by an equivalent homogeneous mixture of these material for determining the few group constants, while the effect of temperature variation in the fuel and coolant density along the axial core direction is considered. All calculations are performed using WIMS and CITATION codes. The obtained results are compared with the results of Final Safety Analysis Report (FSAR) prepared by the designer, and good agreement between the two results is shown.

  19. Temporal and spatial variation in the fouling of silicone coatings in Pearl Harbor, Hawaii.

    Science.gov (United States)

    Holm, E R; Nedved, B T; Phillips, N; Deangelis, K L; Hadfield, M G; Smith, C M

    2000-01-01

    An antifouling or foul-release coating cannot be globally effective if it does not perform well in a range of environmental conditions, against a diversity of fouling organisms. From 1996 to 1998, the field test sites participating in the United States Navy's Office of Naval Research 6.2 Biofouling program examined global variation in the performance of 3 silicone foul-release coatings, viz. GE RTV11, Dow Corning RTV 3140, and Intersleek (International Coatings Ltd), together with a control anticorrosive coating (Ameron Protective Coatings F-150 series). At the University of Hawaii's test site in Pearl Harbor, significant differences were observed among the coatings in the rate of accumulation of fouling. The control coating failed rapidly; after 180-220 d immersion a community dominated by molluscs and sponges developed that persisted for the remainder of the experiment. Fouling of the GE and Dow Corning silicone coatings was slower, but eventually reached a similar community structure and coverage as the control coatings. The Intersleek coating remained lightly fouled throughout the experiment. Spatial variation in the structure of the community fouling the coatings was observed, but not in the extent of fouling. The rate of accumulation of fouling reflected differences among the coatings in adhesion of the tubeworm Hydroides elegans. The surface properties of these coatings may have affected the rate of fouling and the structure of the fouling community through their influence on larval settlement and subsequent interactions with other residents, predators, and the physical environment.

  20. Spatial and temporal snowpack variation in the crown of the continent ecosystem

    Science.gov (United States)

    Selkowitz, D.J.; Fagre, D.B.; Reardon, B.A.

    2002-01-01

    Snowpack related ecosystem changes such as glacier recession and alpine treeline advance have been documented in the Crown of the Continent Ecosystem (CCE) over the course of the previous 150 years. Using data from the Natural Resource Conservation Service's SNOTEL sites and snow course surveys, we examined the spatial and temporal variation in snowpack in the region. SNOTEL data suggest CCE snowpacks are larger and more persistent than in most regions of the Western U.S., and that water year precipitation, rather than mean temperature, is the primary control on April 1 snow water equivalent (SWE). Snow course data indicate a statistically significant downward trend in mean April 1 SWE for the period 1950-2001 but no statistically significant trend in mean May 1 SWE for the longer period 1922-2001. Further analysis reveals that variations in both April 1 and May 1 mean SWE are closely tied to the Pacific Decadal Oscillation, an ENSO-like interdecadal pattern of Pacific Ocean climate variability. Despite no significant trend in mean May 1 SWE between 1922-2001, glaciers in Glacier National Park receded steadily during this period, implying changing climatic conditions crossed a threshold for glacier mass balance maintenace sometime between the Little Ice Age glacial maxima and 1922.

  1. Spatial Distribution of the Coefficient of Variation and Bayesian Forecast for the Paleo-Earthquakes in Japan

    Science.gov (United States)

    Nomura, Shunichi; Ogata, Yosihiko

    2016-04-01

    We propose a Bayesian method of probability forecasting for recurrent earthquakes of inland active faults in Japan. Renewal processes with the Brownian Passage Time (BPT) distribution are applied for over a half of active faults in Japan by the Headquarters for Earthquake Research Promotion (HERP) of Japan. Long-term forecast with the BPT distribution needs two parameters; the mean and coefficient of variation (COV) for recurrence intervals. The HERP applies a common COV parameter for all of these faults because most of them have very few specified paleoseismic events, which is not enough to estimate reliable COV values for respective faults. However, different COV estimates are proposed for the same paleoseismic catalog by some related works. It can make critical difference in forecast to apply different COV estimates and so COV should be carefully selected for individual faults. Recurrence intervals on a fault are, on the average, determined by the long-term slip rate caused by the tectonic motion but fluctuated by nearby seismicities which influence surrounding stress field. The COVs of recurrence intervals depend on such stress perturbation and so have spatial trends due to the heterogeneity of tectonic motion and seismicity. Thus we introduce a spatial structure on its COV parameter by Bayesian modeling with a Gaussian process prior. The COVs on active faults are correlated and take similar values for closely located faults. It is found that the spatial trends in the estimated COV values coincide with the density of active faults in Japan. We also show Bayesian forecasts by the proposed model using Markov chain Monte Carlo method. Our forecasts are different from HERP's forecast especially on the active faults where HERP's forecasts are very high or low.

  2. Estimation of exposure to toxic releases using spatial interaction modeling

    Directory of Open Access Journals (Sweden)

    Conley Jamison F

    2011-03-01

    Full Text Available Abstract Background The United States Environmental Protection Agency's Toxic Release Inventory (TRI data are frequently used to estimate a community's exposure to pollution. However, this estimation process often uses underdeveloped geographic theory. Spatial interaction modeling provides a more realistic approach to this estimation process. This paper uses four sets of data: lung cancer age-adjusted mortality rates from the years 1990 through 2006 inclusive from the National Cancer Institute's Surveillance Epidemiology and End Results (SEER database, TRI releases of carcinogens from 1987 to 1996, covariates associated with lung cancer, and the EPA's Risk-Screening Environmental Indicators (RSEI model. Results The impact of the volume of carcinogenic TRI releases on each county's lung cancer mortality rates was calculated using six spatial interaction functions (containment, buffer, power decay, exponential decay, quadratic decay, and RSEI estimates and evaluated with four multivariate regression methods (linear, generalized linear, spatial lag, and spatial error. Akaike Information Criterion values and P values of spatial interaction terms were computed. The impacts calculated from the interaction models were also mapped. Buffer and quadratic interaction functions had the lowest AIC values (22298 and 22525 respectively, although the gains from including the spatial interaction terms were diminished with spatial error and spatial lag regression. Conclusions The use of different methods for estimating the spatial risk posed by pollution from TRI sites can give different results about the impact of those sites on health outcomes. The most reliable estimates did not always come from the most complex methods.

  3. Spatial variation in particle number size distributions in a large metropolitan area

    Directory of Open Access Journals (Sweden)

    J. F. Mejía

    2007-11-01

    Full Text Available Air quality studies have indicated that particle number size distribution (NSD is unevenly spread in urban air. To date, these studies have focussed on differences in concentration levels between sampling locations rather than differences in the underlying geometries of the distributions. As a result, the existing information on the spatial variation of the NSD in urban areas remains incomplete. To investigate this variation in a large metropolitan area in the southern hemisphere, NSD data collected at nine different locations during different campaigns of varying duration were compared using statistical methods. The spectra were analysed in terms of their modal structures (the graphical representation of the number size distribution function, cumulative distribution and number median diameter (NMD. The study found that with the exception of one site all distributions were bimodal or suggestive of bimodality. In general, peak concentrations were below 30 nm and NMDs below 50 nm, except at a site dominated by diesel trucks, where it shifted to around 50 and 60 nm respectively. Ultrafine particles (UFPs contributed to 82–90% of the particle number, nanoparticles (<50 nm to around 60–70%, except at the diesel traffic site, where their contribution dropped to 50%. Statistical analyses found that the modal structures heterogeneously distributed throughout Brisbane whereas it was not always the case for the NMD. The discussion led to the following site classification: (1 urban sites dominated by petrol traffic, (2 urban sites affected by the proximity to the road and (3 an isolated site dominated by diesel traffic. Comparisons of weekday and weekend data indicated that, the distributions were not statistically different. The only exception occurred at one site, where there is a significant drop in the number of diesel buses on the weekend. The differences in sampling period between sites did not affect the results. The statistics instead suggested

  4. Temporal and spatial variations of particulate matter and gaseous pollutants in the urban area of Tehran

    Science.gov (United States)

    Alizadeh-Choobari, O.; Bidokhti, A. A.; Ghafarian, P.; Najafi, M. S.

    2016-09-01

    Being hemmed in on two sides by high mountains, the urban area of Tehran is characterized by high levels of particulate matter and gaseous pollutants, which have adverse consequences on human health, ecosystems and environment. Using air quality measurements taken in different regions of Tehran, spatial and temporal variations of particulate matter and gaseous pollutants are analyzed to identify the typical climatological aspects of air pollutants. In terms of particulate matter concentrations, South Tehran is more polluted than Central to North Tehran, while West Tehran is more polluted than the East. Concentrations of particles in North Tehran are lower in the midday compared to the midnight, whereas the opposite is true in South Tehran. The observed annual mean concentrations of PM2.5 and PM10 in North Tehran were 37.5 and 76.3 μg m-3, respectively, which are substantially greater than the national annual mean safety limits of 10 μg m-3 for PM2.5 and 20 μg m-3 for PM10. The observed high levels of particulate matter underline the essential need for a coordinated action to reduce the rapidly increasing air pollution over the growing urban area of Tehran. Noticeable monthly (seasonal) variations are evident in the observed PM10 concentrations, with a minimum of 61.5 μg m-3 in March (spring) and a maximum of 82.9 μg m-3 in July (summer), reflecting contribution of weather conditions. Analyzing daily PM2.5 (PM10) concentrations indicate that mid-week Wednesdays (Mondays) are the most polluted days. The higher mid-week concentrations reflect contribution of heavy vehicular traffic, industrial operation and increased commercial activities. Strong diurnal variations in the concentrations of particulate matter in North Tehran are detected, varying from a peak in late night to a minimum in late afternoon, indicating contribution of deeper daytime convective boundary layer and stronger winds in dispersion of particles.

  5. Spatial uncertainty model for visual features using a Kinect™ sensor.

    Science.gov (United States)

    Park, Jae-Han; Shin, Yong-Deuk; Bae, Ji-Hun; Baeg, Moon-Hong

    2012-01-01

    This study proposes a mathematical uncertainty model for the spatial measurement of visual features using Kinect™ sensors. This model can provide qualitative and quantitative analysis for the utilization of Kinect™ sensors as 3D perception sensors. In order to achieve this objective, we derived the propagation relationship of the uncertainties between the disparity image space and the real Cartesian space with the mapping function between the two spaces. Using this propagation relationship, we obtained the mathematical model for the covariance matrix of the measurement error, which represents the uncertainty for spatial position of visual features from Kinect™ sensors. In order to derive the quantitative model of spatial uncertainty for visual features, we estimated the covariance matrix in the disparity image space using collected visual feature data. Further, we computed the spatial uncertainty information by applying the covariance matrix in the disparity image space and the calibrated sensor parameters to the proposed mathematical model. This spatial uncertainty model was verified by comparing the uncertainty ellipsoids for spatial covariance matrices and the distribution of scattered matching visual features. We expect that this spatial uncertainty model and its analyses will be useful in various Kinect™ sensor applications.

  6. Spatial Uncertainty Model for Visual Features Using a Kinect™ Sensor

    Directory of Open Access Journals (Sweden)

    Jae-Han Park

    2012-06-01

    Full Text Available This study proposes a mathematical uncertainty model for the spatial measurement of visual features using Kinect™ sensors. This model can provide qualitative and quantitative analysis for the utilization of Kinect™ sensors as 3D perception sensors. In order to achieve this objective, we derived the propagation relationship of the uncertainties between the disparity image space and the real Cartesian space with the mapping function between the two spaces. Using this propagation relationship, we obtained the mathematical model for the covariance matrix of the measurement error, which represents the uncertainty for spatial position of visual features from Kinect™ sensors. In order to derive the quantitative model of spatial uncertainty for visual features, we estimated the covariance matrix in the disparity image space using collected visual feature data. Further, we computed the spatial uncertainty information by applying the covariance matrix in the disparity image space and the calibrated sensor parameters to the proposed mathematical model. This spatial uncertainty model was verified by comparing the uncertainty ellipsoids for spatial covariance matrices and the distribution of scattered matching visual features. We expect that this spatial uncertainty model and its analyses will be useful in various Kinect™ sensor applications.

  7. Lack of spatial variation of endotoxin in ambient particulate matter across a German metropolitan area

    Science.gov (United States)

    Morgenstern, Verena; Carty, Cara L.; Gehring, Ulrike; Cyrys, Josef; Bischof, Wolfgang; Heinrich, Joachim

    In this study, we describe the spatial variation of endotoxin across an urban setting using Geographic Information Systems (GIS) methods. We also identify potential sources of endotoxin that account for between-site variability and compare endotoxin levels in particulate matter with a 50% aerodynamic cut-off diameter of 2.5 μm (PM 2.5) and of 10 μm (PM 10). In 1999-2000, we collected PM 2.5 and PM 10 in Munich urban air and measured soluble endotoxin concentrations in both particle fractions. Using Teflon filters and Harvard impactors, PM 2.5 was collected at 40 outdoor monitoring sites across Munich and PM 10 at a subset of these sites ( n=12). Approximately four samples were collected at each site for a total of 158 PM 2.5 samples and 48 PM 10 samples. We visited and characterized the surrounding 100 m of each site for potential endotoxin sources. The geometric mean endotoxin concentration for all sites was 1.46 EU mg -1 PM 2.5 (95% confidence intervals (CI): 1.21-1.77) and at the subset of the sites was 1.30 EU mg -1 PM 2.5 (95% CI: 1.01-1.67 EU mg -1 PM 2.5). Endotoxin levels in PM 10 were higher, 3.91 EU mg -1 PM 10 (95% CI: 3.03-5.03 EU mg -1 PM 10), than in PM 2.5 and were moderately correlated, r=0.51. All endotoxin concentrations measured in this study were endotoxin levels (MR: 1.30 for EU mg -1 PM 2.5 and 1.13 for EU m -3 PM 2.5) than sites with no identified sources. Based on the ranges of endotoxin levels at the different sites, we found very little spatial variation in ambient endotoxin concentrations across the metropolitan area of Munich using inverse distance weighting method (IDW) methods ( R2=0.013 for EU mg -1 PM 2.5 and R2=0.020 for EU m -3 PM 2.5). Potential sources of endotoxin surrounding the sites only partly explained the variation seen.

  8. Quantifying spatial disparities in neonatal mortality using a structured additive regression model.

    Directory of Open Access Journals (Sweden)

    Lawrence N Kazembe

    Full Text Available BACKGROUND: Neonatal mortality contributes a large proportion towards early childhood mortality in developing countries, with considerable geographical variation at small areas within countries. METHODS: A geo-additive logistic regression model is proposed for quantifying small-scale geographical variation in neonatal mortality, and to estimate risk factors of neonatal mortality. Random effects are introduced to capture spatial correlation and heterogeneity. The spatial correlation can be modelled using the Markov random fields (MRF when data is aggregated, while the two dimensional P-splines apply when exact locations are available, whereas the unstructured spatial effects are assigned an independent Gaussian prior. Socio-economic and bio-demographic factors which may affect the risk of neonatal mortality are simultaneously estimated as fixed effects and as nonlinear effects for continuous covariates. The smooth effects of continuous covariates are modelled by second-order random walk priors. Modelling and inference use the empirical Bayesian approach via penalized likelihood technique. The methodology is applied to analyse the likelihood of neonatal deaths, using data from the 2000 Malawi demographic and health survey. The spatial effects are quantified through MRF and two dimensional P-splines priors. RESULTS: Findings indicate that both fixed and spatial effects are associated with neonatal mortality. CONCLUSIONS: Our study, therefore, suggests that the challenge to reduce neonatal mortality goes beyond addressing individual factors, but also require to understanding unmeasured covariates for potential effective interventions.

  9. An approach to analyzing environmental drivers to spatial variations in annual distribution of periphytic protozoa in coastal ecosystems.

    Science.gov (United States)

    Xu, Guangjian; Xu, Henglong

    2016-03-15

    The environmental drivers to the spatial variation in annual distribution were studied based on an annual dataset of periphytic protozoa using multivariate approaches. Samples were monthly collected at four stations within a pollution gradient in coastal waters of the Yellow Sea, northern China during a 1-year period. The second-stage (2STAGE) analyses showed that the internal patterns of the annual distribution were changed along the pollution gradient in terms of abundance. The dominant species represented different succession dynamics among four sampling stations during a 1-year cycle. Best matching analysis demonstrated that the spatial variations in annual distribution of the protozoa were significantly correlated with ammonium nitrogen (NH4-N), alone or in combination with salinity and dissolved oxygen (DO). Based on the results, we suggest that the nutrients, salinity and DO may be the main drivers to shape the spatial variations in annual distribution of periphytic protozoa.

  10. 63Cu NQR evidence for spatial variation of hole concentration in La2-xSrxCuO4.

    Science.gov (United States)

    Singer, P M; Hunt, A W; Imai, T

    2002-01-28

    We report experimental evidence for the spatial variation of hole concentration x(hole) in the high T(c) superconductor La2-xSrxCuO4 ( 0.04 NQR using 63Cu isotope enriched samples. We demonstrate that the extent of the spatial variation of the local hole concentration Delta(x)hole is reflected on (63)1/T1 and deduce the temperature dependence. Delta(x)hole increases below 500-600 K, and reaches values as large as Delta(x)hole/x approximately 0.5 below approximately 150 K. We estimate the length scale of the spatial variation in x(hole) to be R(hole) greater, similar 3 nm from an analysis of the NQR spectrum.

  11. Including spatial data in nutrient balance modelling on dairy farms

    Science.gov (United States)

    van Leeuwen, Maricke; van Middelaar, Corina; Stoof, Cathelijne; Oenema, Jouke; Stoorvogel, Jetse; de Boer, Imke

    2017-04-01

    The Annual Nutrient Cycle Assessment (ANCA) calculates the nitrogen (N) and phosphorus (P) balance at a dairy farm, while taking into account the subsequent nutrient cycles of the herd, manure, soil and crop components. Since January 2016, Dutch dairy farmers are required to use ANCA in order to increase understanding of nutrient flows and to minimize nutrient losses to the environment. A nutrient balance calculates the difference between nutrient inputs and outputs. Nutrients enter the farm via purchased feed, fertilizers, deposition and fixation by legumes (nitrogen), and leave the farm via milk, livestock, manure, and roughages. A positive balance indicates to which extent N and/or P are lost to the environment via gaseous emissions (N), leaching, run-off and accumulation in soil. A negative balance indicates that N and/or P are depleted from soil. ANCA was designed to calculate average nutrient flows on farm level (for the herd, manure, soil and crop components). ANCA was not designed to perform calculations of nutrient flows at the field level, as it uses averaged nutrient inputs and outputs across all fields, and it does not include field specific soil characteristics. Land management decisions, however, such as the level of N and P application, are typically taken at the field level given the specific crop and soil characteristics. Therefore the information that ANCA provides is likely not sufficient to support farmers' decisions on land management to minimize nutrient losses to the environment. This is particularly a problem when land management and soils vary between fields. For an accurate estimate of nutrient flows in a given farming system that can be used to optimize land management, the spatial scale of nutrient inputs and outputs (and thus the effect of land management and soil variation) could be essential. Our aim was to determine the effect of the spatial scale of nutrient inputs and outputs on modelled nutrient flows and nutrient use efficiencies

  12. Full feature data model for spatial information network integration

    Institute of Scientific and Technical Information of China (English)

    DENG Ji-qiu; BAO Guang-shu

    2006-01-01

    In allusion to the difficulty of integrating data with different models in integrating spatial information,the characteristics of raster structure, vector structure and mixed model were analyzed, and a hierarchical vectorraster integrative full feature model was put forward by integrating the advantage of vector and raster model and using the object-oriented method. The data structures of the four basic features, i.e. point, line, surface and solid,were described. An application was analyzed and described, and the characteristics of this model were described. In this model, all objects in the real world are divided into and described as features with hierarchy, and all the data are organized in vector. This model can describe data based on feature, field, network and other models, and avoid the disadvantage of inability to integrate data based on different models and perform spatial analysis on them in spatial information integration.

  13. FUEL3-D: A Spatially Explicit Fractal Fuel Distribution Model

    Science.gov (United States)

    Russell A. Parsons

    2006-01-01

    Efforts to quantitatively evaluate the effectiveness of fuels treatments are hampered by inconsistencies between the spatial scale at which fuel treatments are implemented and the spatial scale, and detail, with which we model fire and fuel interactions. Central to this scale inconsistency is the resolution at which variability within the fuel bed is considered. Crown...

  14. Estimating spatial variations in soil water content from electrical conductivity surveys across semiarid Mediterranean agrosystems

    Science.gov (United States)

    Mekki, Insaf; Jaiez, Zeineb; Jacob, Frédéric

    2014-05-01

    was close to permanent wilting point. Soil ECa may provide useful information for assessing variation in soil water content across Lebna catchment in the Cap Bon region in Mediterranean conditions and other regions with similar characteristics. The further testing of the procedure with intensive soil sampling by landscape position may improve the ability of the calibration equations to infer SWC and map its spatial variability.

  15. An Improved Direction Relation Detection Model for Spatial Objects

    Institute of Scientific and Technical Information of China (English)

    FENG Yucai; YI Baolin

    2004-01-01

    Direction is a common spatial concept that is used in our daily life. It is frequently used as a selection condition in spatial queries. As a result, it is important for spatial databases to provide a mechanism for modeling and processing direction queries and reasoning. Depending on the direction relation matrix, an inverted direction relation matrix and the concept of direction pre- dominance are proposed to improve the detection of direction relation between objects. Direction predicates of spatial systems are also extended. These techniques can improve the veracity of direction queries and reasoning. Experiments show excellent efficiency and performance in view of direction queries.

  16. Spatial variation in organic matter utilization by benthic communities from Yura River-Estuary to offshore of Tango Sea, Japan

    Science.gov (United States)

    Antonio, Emily S.; Kasai, Akihide; Ueno, Masahiro; Won, Nam-il; Ishihi, Yuka; Yokoyama, Hisashi; Yamashita, Yoh

    2010-01-01

    We investigated the distribution of δ 13C and δ 15N of organic matter among benthic communities from the upper estuary of Yura River to offshore of Tango Sea, Japan, to determine spatial variation in utilization of organic matter by benthic communities. The δ 13C values of benthic animals ranged from -27 to -15‰ in the upper estuary, -21 to -15‰ in the lower estuary, -20 to -16‰ in the shallow coast (5-10 m depths), -18 to -16‰ in the deep coast (30-60 m depths) and -19 to -15‰ in offshore (100-150 m depths) stations. Adapting the dual isotope values to mixing models, we estimated the relative contributions of potential food sources to the benthos diet. Phytoplankton and macroalgae that intruded the estuary in summer were utilized as alternative food aside from the terrestrial-origin organic matter assimilated by the estuarine benthic consumers. Resuspended benthic microalgae were important source of energy in the shallow coastal stations, while abundant supply of phytodetritus fueled the deep coastal and offshore benthic food webs. Spatial difference in the diet of benthic communities depends largely on the shifts in the primary carbon source. Thus, benthic communities are important link of autochthonous/allochthonous production and secondary production in the continuous river-estuary-marine system.

  17. 30th International School of Mathematics "G Stampacchia" : Equilibrium Problems and Variational Models "Ettore Majorana"

    CERN Document Server

    Giannessi, Franco; Maugeri, Antonino; Equilibrium Problems and Variational Models

    2000-01-01

    The volume, devoted to variational analysis and its applications, collects selected and refereed contributions, which provide an outline of the field. The meeting of the title "Equilibrium Problems and Variational Models", which was held in Erice (Sicily) in the period June 23 - July 2 2000, was the occasion of the presentation of some of these papers; other results are a consequence of a fruitful and constructive atmosphere created during the meeting. New results, which enlarge the field of application of variational analysis, are presented in the book; they deal with the vectorial analysis, time dependent variational analysis, exact penalization, high order deriva­ tives, geometric aspects, distance functions and log-quadratic proximal methodology. The new theoretical results allow one to improve in a remarkable way the study of significant problems arising from the applied sciences, as continuum model of transportation, unilateral problems, multicriteria spatial price models, network equilibrium...

  18. Spatial analysis of toxic emissions in LCA: a sub-continental nested USEtox model with freshwater archetypes.

    Science.gov (United States)

    Kounina, Anna; Margni, Manuele; Shaked, Shanna; Bulle, Cécile; Jolliet, Olivier

    2014-08-01

    This paper develops continent-specific factors for the USEtox model and analyses the accuracy of different model architectures, spatial scales and archetypes in evaluating toxic impacts, with a focus on freshwater pathways. Inter-continental variation is analysed by comparing chemical fate and intake fractions between sub-continental zones of two life cycle impact assessment models: (1) the nested USEtox model parameterized with sub-continental zones and (2) the spatially differentiated IMPACTWorld model with 17 interconnected sub-continental regions. Substance residence time in water varies by up to two orders of magnitude among the 17 zones assessed with IMPACTWorld and USEtox, and intake fraction varies by up to three orders of magnitude. Despite this variation, the nested USEtox model succeeds in mimicking the results of the spatially differentiated model, with the exception of very persistent volatile pollutants that can be transported to polar regions. Intra-continental variation is analysed by comparing fate and intake fractions modelled with the a-spatial (one box) IMPACT Europe continental model vs. the spatially differentiated version of the same model. Results show that the one box model might overestimate chemical fate and characterisation factors for freshwater eco-toxicity of persistent pollutants by up to three orders of magnitude for point source emissions. Subdividing Europe into three archetypes, based on freshwater residence time (how long it takes water to reach the sea), improves the prediction of fate and intake fractions for point source emissions, bringing them within a factor five compared to the spatial model. We demonstrated that a sub-continental nested model such as USEtox, with continent-specific parameterization complemented with freshwater archetypes, can thus represent inter- and intra-continental spatial variations, whilst minimizing model complexity.

  19. The temporal and spatial characteristics of the surface air temperature variations over the Antarctic and its surrounding area

    Institute of Scientific and Technical Information of China (English)

    陆龙骅; 卞林根; 贾朋群

    1997-01-01

    The characteristics of the spatial distribution, temporal variations trend and oscillation for the surface air temperature variations during 1957-1993 in the Antarctic and its surrounding area were analyzed. The results show that the short-time climate change in the Antarctic is complex both temporally and spatially. The Antarctic is by no means the strongest responding region to the global greenhouse effect. There is a distinguished difference in the trends of the temperature changes for the Antarctic and global mean, which could not be explained simply by the global greenhouse effect.

  20. Spatial Statistical Procedures to Validate Input Data in Energy Models

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, G.; Stewart, J.; Barr, C.; Brady Sabeff, L.; George, R.; Heimiller, D.; Milbrandt, A.

    2006-01-01

    Energy modeling and analysis often relies on data collected for other purposes such as census counts, atmospheric and air quality observations, economic trends, and other primarily non-energy related uses. Systematic collection of empirical data solely for regional, national, and global energy modeling has not been established as in the abovementioned fields. Empirical and modeled data relevant to energy modeling is reported and available at various spatial and temporal scales that might or might not be those needed and used by the energy modeling community. The incorrect representation of spatial and temporal components of these data sets can result in energy models producing misleading conclusions, especially in cases of newly evolving technologies with spatial and temporal operating characteristics different from the dominant fossil and nuclear technologies that powered the energy economy over the last two hundred years. Increased private and government research and development and public interest in alternative technologies that have a benign effect on the climate and the environment have spurred interest in wind, solar, hydrogen, and other alternative energy sources and energy carriers. Many of these technologies require much finer spatial and temporal detail to determine optimal engineering designs, resource availability, and market potential. This paper presents exploratory and modeling techniques in spatial statistics that can improve the usefulness of empirical and modeled data sets that do not initially meet the spatial and/or temporal requirements of energy models. In particular, we focus on (1) aggregation and disaggregation of spatial data, (2) predicting missing data, and (3) merging spatial data sets. In addition, we introduce relevant statistical software models commonly used in the field for various sizes and types of data sets.

  1. Spatial Statistical Procedures to Validate Input Data in Energy Models

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Livermore National Laboratory

    2006-01-27

    Energy modeling and analysis often relies on data collected for other purposes such as census counts, atmospheric and air quality observations, economic trends, and other primarily non-energy-related uses. Systematic collection of empirical data solely for regional, national, and global energy modeling has not been established as in the above-mentioned fields. Empirical and modeled data relevant to energy modeling is reported and available at various spatial and temporal scales that might or might not be those needed and used by the energy modeling community. The incorrect representation of spatial and temporal components of these data sets can result in energy models producing misleading conclusions, especially in cases of newly evolving technologies with spatial and temporal operating characteristics different from the dominant fossil and nuclear technologies that powered the energy economy over the last two hundred years. Increased private and government research and development and public interest in alternative technologies that have a benign effect on the climate and the environment have spurred interest in wind, solar, hydrogen, and other alternative energy sources and energy carriers. Many of these technologies require much finer spatial and temporal detail to determine optimal engineering designs, resource availability, and market potential. This paper presents exploratory and modeling techniques in spatial statistics that can improve the usefulness of empirical and modeled data sets that do not initially meet the spatial and/or temporal requirements of energy models. In particular, we focus on (1) aggregation and disaggregation of spatial data, (2) predicting missing data, and (3) merging spatial data sets. In addition, we introduce relevant statistical software models commonly used in the field for various sizes and types of data sets.

  2. A Spatially Distributed Hydrological Model For The Okavango Delta, Botswana

    Science.gov (United States)

    Bauer, P.; Kinzelbach, W.; Thabeng, G.

    2003-04-01

    The Okavango Delta is a large (˜30 000 km^2) inland delta situated in northern Botswana. It is subject to annual flooding due to the strong seasonality of the inflowing Okavango River and of local rainfall. The inflowing waters spread out over vast perennial and seasonal floodplains and partially infiltrate into the underlying sand aquifer. Ultimately, the water is consumed by evapotranspiration, there is no significant outflow from the Delta. The system's response to the annual flood in the Okavango River as well as local rainfall and evapotranspiration is modelled within a finite difference scheme based on MODFLOW. The wetland and the underlying sand aquifer are incorporated as two separate layers. In the superficial layer, either steady uniform channel flow (Darcy-Weisbach equation) or potential flow (Darcy flow) can be chosen on a cell-by-cell basis. The coarse spatial resolution does not capture the small-scale variation in the topographic elevation. Therefore, upscaling techniques are applied to incorporate the statistics of that variation into effective parameters for the hydraulic conductivity, the storage coefficient and the evapotranspiration. Modelled flooding patterns are compared with flooding patterns derived from NOAA-AVHRR and other remote sensing data (1 km resolution). Good correspondence between the two is achieved based on parameters chosen according to prior knowledge and field data. Global indicators like the average size of the Delta and the temporal variance of its size are closely reproduced. Ultimately, the remotely sensed flooding patterns will be used to calibrate the model. Apart from flooding patterns, model outputs include cell-by-cell flow terms. Water balances can be calculated for arbitrary sub-regions of the grid. Other monitoring data like water levels in rivers and boreholes as well as discharges at gauging points may be used for validation of the model. The Okavango Delta is one of the prime conservation areas in Africa and a

  3. Physically-based modeling of topographic effects on spatial evapotranspiration and soil moisture patterns through radiation and wind

    Directory of Open Access Journals (Sweden)

    M. Liu

    2012-02-01

    Full Text Available In this paper, simulations with the Soil Water Atmosphere Plant (SWAP model are performed to quantify the spatial variability of both potential and actual evapotranspiration (ET, and soil moisture content (SMC caused by topography-induced spatial wind and radiation differences. To obtain the spatially distributed ET/SMC patterns, the field scale SWAP model is applied in a distributed way for both pointwise and catchment wide simulations. An adapted radiation model from r.sun and the physically-based meso-scale wind model METRAS PC are applied to obtain the spatial radiation and wind patterns respectively, which show significant spatial variation and correlation with aspect and elevation respectively. Such topographic dependences and spatial variations further propagate to ET/SMC. A strong spatial, seasonal-dependent, scale-relevant intra-catchment variability in daily/annual ET and less variability in SMC can be observed from the numerical experiments. The study concludes that topography has a significant effect on ET/SMC in the humid region where ET is a energy limited rather than water availability limited process. It affects the spatial runoff generation through spatial radiation and wind, therefore should be applied to inform hydrological model development. In addition, the methodology used in the study can serve as a general method for physically-based ET estimation for data sparse regions.

  4. Diploptene δ13C values from contemporary thermokarst lake sediments show complex spatial variation

    Science.gov (United States)

    Davies, Kimberley L.; Pancost, Richard D.; Edwards, Mary E.; Anthony, Katey M. Walter; Langdon, Peter G.; Chaves Torres, Lidia

    2016-05-01

    Cryospheric changes in northern high latitudes are linked to significant greenhouse gas flux to the atmosphere, for example, methane that originates from organic matter decomposition in thermokarst lakes. The set of pathways that link methane production in sediments, via oxidation in the lake system, to the flux of residual methane to the atmosphere is complex and exhibits temporal and spatial variation. The isotopic signal of bacterial biomarkers (hopanoids, e.g. diploptene) in sediments has been used to identify contemporary ocean-floor methane seeps and, in the geological record, periods of enhanced methane production (e.g. the PETM). The biomarker approach could potentially be used to assess temporal changes in lake emissions through the Holocene via the sedimentary biomarker record. However, there are no data on the consistency of the signal of isotopic depletion in relation to source or on the amount of noise (unexplained variation) in biomarker values from modern lake sediments. We assessed methane oxidation as represented by the isotopic signal of biomarkers from methane oxidising bacteria (MOB) in multiple surface sediment samples in three distinct areas known to emit varying levels of methane in two shallow Alaskan thermokarst lakes. Diploptene was present and had δ13C values lower than -38 ‰ in all sediments analysed, suggesting methane oxidation was widespread. However, there was considerable variation in δ13C values within each area. The most 13C-depleted diploptene was found in an area of high methane ebullition in Ace Lake (diploptene δ13C values between -68.2 and -50.1 ‰). In contrast, significantly higher diploptene δ13C values (between -42.9 and -38.8 ‰) were found in an area of methane ebullition in Smith Lake. δ13C values of diploptene between -56.8 and -46.9 ‰ were found in the centre of Smith Lake, where ebullition rates are low but diffusive methane efflux occurs. The small-scale heterogeneity of the samples may reflect patchy

  5. Spatial-temporal patterns and driving mechanisms of semiannual variations in the Philippine Sea

    Science.gov (United States)

    Zhao, Jun; Li, Yuanlong; Wang, Fan; Zhai, Fangguo; Yu, Xiaolin

    2012-10-01

    Satellite altimetric sea surface height (SSH) measurements from 1992 through 2010 are used to explore the oceanic semiannual variations in the Philippine Sea (PS). Pronounced semiannual SSH variations are detected within two zonal bands. One lies east of Luzon Strait (19°-22°N) in the northern PS, while the other is southeast of Mindanao coast (4°-7°N) in the southern PS. In the two near-coast boxes where semiannual harmonic amplitude exceeds 4 cm, the northern box (127°-133°E, 19°-22°N) and the southern box (127°-133°E, 4°-7°N), semiannual changes contribute considerably to the total annual SSH variance by 12% and 17%, respectively. Despite prominent SSH variability, the bifurcation latitude of the North Equatorial Current (NBL) exhibits weak fluctuations with a peak-to-peak difference of only 0.3° on semiannual time scale. While the in-phase annual SSH variations between the two boxes work together to enhance annual NBL changes, their out-of-phase semiannual SSH variations offset each other in driving the NBL displacements. Further analysis with a 11/2-layer reduced-gravity model forced by ECMWF wind stress reveals that the observed semiannual SSH variations are primarily driven by local wind forcing in the far western Pacific. Rossby wave signals propagating from the eastern/central Pacific contribute much less due to along-path dispersion and cancellation. Semiannual signals of wind field in the northern PS reflect mainly the semiannual changes of the Asian Monsoon system, while those in the southern PS arise from the combined effects of Monsoon transition and the annual migration of the intertropical convergence zone (ITCZ).

  6. 基于CFD的温室气温时空变化预测模型及通风调控措施%Prediction model on temporal and spatial variation of air temperature in greenhouse and ventilation control measures based on CFD

    Institute of Scientific and Technical Information of China (English)

    任守纲; 杨薇; 王浩云; 薛卫; 徐焕良; 熊迎军

    2015-01-01

    夏季温室高温湿热,对作物生长产生重大危害,制定合理的夏季温室气温调控方案,是提高温室生产效益,降低温室气温调控能耗的关键问题。该文基于计算流体力学(computational fluid dynamics,CFD)方法,结合气象预报信息,针对苏南地区大型连栋温室,建立了夏季温室气温时空变化预测模型,通过设置边界参数,对不同通风条件下温室气温的时空变化进行了预测,并通过试验验证了模型的有效性。试验结果表明,预测值与实测值吻合良好,均方根误差在1.2℃以内,最大相对误差在6%以内,平均相对误差在4%以内。不同通风降温条件下的试验结果显示,温室气温空间分布存在明显差异,湿帘-风机系统较自然通风降温效果显著,降温幅度在5℃左右,持续的湿帘-风机降温措施可将温室高温控制在较低水平。基于该文模型的预测结果和温室调控目标,选取合适的时间点、时间长度和不同类型的通风降温措施,可有效提高温室气温调控效率和效益。同时,该研究还可为优化传感器布局提供依据。%Hot and humid environment inside greenhouse in summer is a major threat to crop growth. How to make reasonable control schemes of greenhouse air temperature in summer is the key to improve the greenhouse production efficiency and reduce the energy consumption. In this study, we established a prediction model on temporal and spatial variation of air temperature in greenhouse based on the computational fluid dynamics (CFD) method and meteorology forecast information. The prediction model was adapted to the large multi-span plastic greenhouse in the southern regions of Jiangsu under the natural ventilation and fan-pad cooling system. It can predict the spatial and temporal distribution of greenhouse air temperature under different ventilation cooling conditions. The numerical computation of this

  7. Small-scale spatial variation in population dynamics and fishermen response in a coastal marine fishery.

    Directory of Open Access Journals (Sweden)

    Jono R Wilson

    Full Text Available A major challenge for small-scale fisheries management is high spatial variability in the demography and life history characteristics of target species. Implementation of local management actions that can reduce overfishing and maximize yields requires quantifying ecological heterogeneity at small spatial scales and is therefore limited by available resources and data. Collaborative fisheries research (CFR is an effective means to collect essential fishery information at local scales, and to develop the social, technical, and logistical framework for fisheries management innovation. We used a CFR approach with fishing partners to collect and analyze geographically precise demographic information for grass rockfish (Sebastes rastrelliger, a sedentary, nearshore species harvested in the live fish fishery on the West Coast of the USA. Data were used to estimate geographically distinct growth rates, ages, mortality, and length frequency distributions in two environmental subregions of the Santa Barbara Channel, CA, USA. Results indicated the existence of two subpopulations; one located in the relatively cold, high productivity western Channel, and another in the relatively warm, low productivity eastern Channel. We parameterized yield per recruit models, the results of which suggested nearly twice as much yield per recruit in the high productivity subregion relative to the low productivity subregion. The spatial distribution of fishing in the two environmental subregions demonstrated a similar pattern to the yield per recruit outputs with greater landings, effort, and catch per unit effort in the high productivity subregion relative to the low productivity subregion. Understanding how spatial variability in stock dynamics translates to variability in fishery yield and distribution of effort is important to developing management plans that maximize fishing opportunities and conservation benefits at local scales.

  8. A sensitivity analysis using different spatial resolution terrain models and flood inundation models

    Science.gov (United States)

    Papaioannou, George; Aronica, Giuseppe T.; Loukas, Athanasios; Vasiliades, Lampros

    2014-05-01

    The impact of terrain spatial resolution and accuracy on the hydraulic flood modeling can pervade the water depth and the flood extent accuracy. Another significant factor that can affect the hydraulic flood modeling outputs is the selection of the hydrodynamic models (1D,2D,1D/2D). Human mortality, ravaged infrastructures and other damages can be derived by extreme flash flood events that can be prevailed in lowlands at suburban and urban areas. These incidents make the necessity of a detailed description of the terrain and the use of advanced hydraulic models essential for the accurate spatial distribution of the flooded areas. In this study, a sensitivity analysis undertaken using different spatial resolution of Digital Elevation Models (DEMs) and several hydraulic modeling approaches (1D, 2D, 1D/2D) including their effect on the results of river flow modeling and mapping of floodplain. Three digital terrain models (DTMs) were generated from the different elevation variation sources: Terrestrial Laser Scanning (TLS) point cloud data, classic land surveying and digitization of elevation contours from 1:5000 scale topographic maps. HEC-RAS and MIKE 11 are the 1-dimensional hydraulic models that are used. MLFP-2D (Aronica et al., 1998) and MIKE 21 are the 2-dimensional hydraulic models. The last case consist of the integration of MIKE 11/MIKE 21 where 1D-MIKE 11 and 2D-MIKE 21 hydraulic models are coupled through the MIKE FLOOD platform. The validation process of water depths and flood extent is achieved through historical flood records. Observed flood inundation areas in terms of simulated maximum water depth and flood extent were used for the validity of each application result. The methodology has been applied in the suburban section of Xerias river at Volos-Greece. Each dataset has been used to create a flood inundation map for different cross-section configurations using different hydraulic models. The comparison of resulting flood inundation maps indicates

  9. Landscape-scale spatial heterogeneity in phytodetrital cover and megafauna biomass in the abyss links to modest topographic variation

    Science.gov (United States)

    Morris, Kirsty J.; Bett, Brian J.; Durden, Jennifer M.; Benoist, Noelie M. A.; Huvenne, Veerle A. I.; Jones, Daniel O. B.; Robert, Katleen; Ichino, Matteo C.; Wolff, George A.; Ruhl, Henry A.

    2016-09-01

    Sinking particulate organic matter (POM, phytodetritus) is the principal limiting resource for deep-sea life. However, little is known about spatial variation in POM supply to the abyssal seafloor, which is frequently assumed to be homogenous. In reality, the abyss has a highly complex landscape with millions of hills and mountains. Here, we show a significant increase in seabed POM % cover (by ~1.05 times), and a large significant increase in megafauna biomass (by ~2.5 times), on abyssal hill terrain in comparison to the surrounding plain. These differences are substantially greater than predicted by current models linking water depth to POM supply or benthic biomass. Our observed variations in POM % cover (phytodetritus), megafauna biomass, sediment total organic carbon and total nitrogen, sedimentology, and benthic boundary layer turbidity, all appear to be consistent with topographically enhanced current speeds driving these enhancements. The effects are detectable with bathymetric elevations of only 10 s of metres above the surrounding plain. These results imply considerable unquantified heterogeneity in global ecology.

  10. Interpretation of spatial and temporal variations of hydrogen quadrupole absorptions in the Jovian atmosphere observed during the 1972 apparition

    Science.gov (United States)

    Hunt, G. E.; Bergstralh, J. T.

    1977-01-01

    Results are reported for a systematic investigation of temporal and spatial variations of hydrogen quadrupole lines formed in the Jovian atmosphere, which was performed by measuring the strengths of the S(1) lines of H2 (3,0) and (4,0) quadrupole bands at several points on the Jovian disk during the 1972 apparition. The observations support the hypothesis that the strength of the (3,0) S(1) line varies significantly with time, suggest the possibility of short-term temporal variation in the strength of the (4,0) line, and indicate that the H2 line strengths vary remarkably little from limb to limb in the equatorial region. A Galatry line-shape profile is calculated, and a radiative-transfer analysis is carried out using the Henyey-Greenstein phase function for single particle scattering. It is shown that the observations are consistent with a multilayer atmospheric model having an optically thin upper cloud deck separated by a stratum of nonscattering gas from an optically thick lower cloud.

  11. Spatial-temporal variations of surface ozone and ozone control strategy for Northern China

    Directory of Open Access Journals (Sweden)

    G. Tang

    2011-09-01

    Full Text Available The Project of Atmospheric Combined Pollution Monitoring over Beijing and its Surrounding Areas, was an intensive field campaign conducted over northern China between June 2009 and September 2011 to provide an in-depth understanding and a comprehensive record of ozone (O3, respirable suspended particulate (PM10, fine particle (PM2.5, nitrogen oxides (NOx, volatile organic compounds (VOCs and other air pollutants in this quickly developing region of China. In this campaign, 25 stations in an air-quality monitoring network provided regional-scale spatial coverage. In this study, we analyzed the data on O3 and NOx levels obtained at the 22 sites over northern China between 1 September 2009 and 31 August 2010. Our goal was to investigate the O3 spatial-temporal variations and control strategy in this area. Significant diurnal, and seasonal variations were noted, with the highest concentrations typically found at around 03:00 p.m. (LT and in June. The lowest concentrations were generally found during early morning hours (around 06:00 a.m. and in December. Compared with July and August, June has increased photochemical production due to decreasing cloudiness coupled with reduced O3 loss due to less dry deposition, inducing an O3 peak appearing in June. The averaged O3 concentrations were lower in the plains area compared with the mountainous area due to the titration effects of high NOx emissions in urban areas. When the characteristics of O3 pollution in different regions were distinguished by factor analysis, we found high levels of O3 that exceeded China's National Standard throughout the plains areas, especially over Beijing and the surrounding areas. An integrated analysis with emissions data, meteorological data, and topography over northern China found that the meteorological results were the

  12. Study on spatial temporal model in property management information system

    Institute of Scientific and Technical Information of China (English)

    李良宝; 李晓东

    2004-01-01

    Time is an important dimension for information in the geographical information system. Data, such as the historical state of target property space and related events causing the state to be changed, should be saved as important files. This should be applied to property management. This paper designs and constructs a spatial temporal model, which is suitable to the property data changing management and spatial temporal query by analyzing the basic types and characteristics of property management spatial changing time and date. This model uses current and historical situational layers to organize and set up the relationship between current situation data and historical dates according to spatial temporal topological relations in property entities. By using Map Basic, housing property management and spatial query is realized.

  13. Spatial variations in daily average CO2 concentrations above wetland surface of Xianghai National Nature Reserve, China

    Institute of Scientific and Technical Information of China (English)

    BAI Jun-hong; OUYANG Hua; WANG Qing-gai; ZHOU Cai-ping; XU Xiao-feng

    2005-01-01

    Horizontal and vertical variations of daily average CO2 concentration above the wetland surface were studied in Xianghai National Nature Reserve of China in August, 2000. The primary purpose was to study spatial distribution characteristics of CO2 concentration on the four levels of height(0. 1 m, 0.6 m, 1.2 m and 2 m) and compare the differences of CO2 concentration under different land covers. Results showed that daily average CO2 concentration above wetland surface in Xianghai National Natural Reserve was lower than that above other wetlands in northeast China as well as the worldwide average, suggesting that Xianghai wetland absorbed CO2 in August and acted as"sink" of CO2. The horizontal variations on the four levels of height along the latitude were distinct, and had the changing tendency of"decreasing after increasing" with the increase of height. The areas with obvious variations were consistent on different levels of height,and those with the highest variations appeared above surface of shore, sloping field, Typha wetland and Phragmites wetland; the vertical variations were greatly different, with the higher variations in Phragmites wetland and Typha wetland, and the lands near the shore and the sloping field with the lower variations. Spatial variations of daily average CO2 concentrations above wetland surface were affected by surface qualities and land covers.

  14. Spatial Distribution of the Errors in Modeling the Mid-Latitude Critical Frequencies by Different Models

    Science.gov (United States)

    Kilifarska, N. A.

    There are some models that describe the spatial distribution of greatest frequency yielding reflection from the F2 ionospheric layer (foF2). However, the distribution of the models' errors over the globe and how they depend on seasons, solar activity, etc., are unknown till this time. So the aim of the present paper is to compare the accuracy in describing the latitudinal and longitudinal variation of the mid-latitude maximum electron density, of CCIR, URSI, and a new created theoretical model. A comparison between the above mentioned models and all available from Boulder's data bank VI data (among 35 deg and 70 deg) have been made. Data for three whole years with different solar activity - 1976 (F_10.7 = 73.6), 1981 (F_10.7 = 20.6), 1983 (F_10.7 = 119.6) have been compared. The final results show that: 1. the areas with greatest and smallest errors depend on UT, season and solar activity; 2. the error distribution of CCIR and URSI models are very similar and are not coincident with these ones of theoretical model. The last result indicates that the theoretical model, described briefly bellow, may be a real alternative to the empirical CCIR and URSI models. The different spatial distribution of the models' errors gives a chance for the users to choose the most appropriate model, depending on their needs. Taking into account that the theoretical models have equal accuracy in region with many or without any ionosonde station, this result shows that our model can be used to improve the global mapping of the mid-latitude ionosphere. Moreover, if Re values of the input aeronomical parameters (neutral composition, temperatures and winds), are used - it may be expected that this theoretical model can be applied for Re or almost Re-time mapping of the main ionospheric parameters (foF2 and hmF2).

  15. Regression-based air temperature spatial prediction models: an example from Poland

    Directory of Open Access Journals (Sweden)

    Mariusz Szymanowski

    2013-10-01

    Full Text Available A Geographically Weighted Regression ? Kriging (GWRK algorithm, based on the local Geographically Weighted Regression (GWR, is applied for spatial prediction of air temperature in Poland. Hengl's decision tree for selecting a suitable prediction model is extended for varying spatial relationships between the air temperature and environmental predictors with an assumption of existing environmental dependence of analyzed temperature variables. The procedure includes the potential choice of a local GWR instead of the global Multiple Linear Regression (MLR method for modeling the deterministic part of spatial variation, which is usual in the standard regression (residual kriging model (MLRK. The analysis encompassed: testing for environmental correlation, selecting an appropriate regression model, testing for spatial autocorrelation of the residual component, and validating the prediction accuracy. The proposed approach was performed for 69 air temperature cases, with time aggregation ranging from daily to annual average air temperatures. The results show that, irrespective of the level of data aggregation, the spatial distribution of temperature is better fitted by local models, and hence is the reason for choosing a GWR instead of the MLR for all variables analyzed. Additionally, in most cases (78% there is spatial autocorrelation in the residuals of the deterministic part, which suggests that the GWR model should be extended by ordinary kriging of residuals to the GWRK form. The decision tree used in this paper can be considered as universal as it encompasses either spatially varying relationships of modeled and explanatory variables or random process that can be modeled by a stochastic extension of the regression model (residual kriging. Moreover, for all cases analyzed, the selection of a method based on the local regression model (GWRK or GWR does not depend on the data aggregation level, showing the potential versatility of the technique.

  16. Scale-based spatial data model for GIS

    Institute of Scientific and Technical Information of China (English)

    WEI Zu-kuan

    2004-01-01

    Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.

  17. Spatial modelling of wind speed around windbreaks

    NARCIS (Netherlands)

    Vigiak, O.; Sterk, G.; Warren, A.; Hagen, L.J.

    2003-01-01

    This paper presents a model to integrate windbreak shelter effects into a Geographic Information System (GIS). The GIS procedure incorporates the 1999 version windbreak sub-model of the Wind Erosion Prediction System (WEPS). Windbreak shelter is modeled in terms of friction velocity reduction, which

  18. Total Variation Based Perceptual Image Quality Assessment Modeling

    Directory of Open Access Journals (Sweden)

    Yadong Wu

    2014-01-01

    Full Text Available Visual quality measure is one of the fundamental and important issues to numerous applications of image and video processing. In this paper, based on the assumption that human visual system is sensitive to image structures (edges and image local luminance (light stimulation, we propose a new perceptual image quality assessment (PIQA measure based on total variation (TV model (TVPIQA in spatial domain. The proposed measure compares TVs between a distorted image and its reference image to represent the loss of image structural information. Because of the good performance of TV model in describing edges, the proposed TVPIQA measure can illustrate image structure information very well. In addition, the energy of enclosed regions in a difference image between the reference image and its distorted image is used to measure the missing luminance information which is sensitive to human visual system. Finally, we validate the performance of TVPIQA measure with Cornell-A57, IVC, TID2008, and CSIQ databases and show that TVPIQA measure outperforms recent state-of-the-art image quality assessment measures.

  19. On the importance of modelling the internal spatial dynamics of biological cells.

    Science.gov (United States)

    Sayyid, Faiz; Kalvala, Sara

    2016-07-01

    Spatial effects such as cell shape have very often been considered negligible in models of cellular pathways, and many existing simulation infrastructures do not take such effects into consideration. Recent experimental results are reversing this judgement by showing that very small spatial variations can make a big difference in the fate of a cell. This is particularly the case when considering eukaryotic cells, which have a complex physical structure and many subtle control mechanisms, but bacteria are also interesting for the huge variation in shape both between species and in different phases of their lifecycle. In this work we perform simulations that measure the effect of three common bacterial shapes on the behaviour of model cellular pathways. To perform these experiments we develop ReDi-Cell, a highly scalable GPGPU cell simulation infrastructure for the modelling of cellular pathways in spatially detailed environments. ReDi-Cell is validated against known-good simulations, prior to its use in new work. We then use ReDi-Cell to conduct novel experiments that demonstrate the effect that three common bacterial shapes (Cocci, Bacilli and Spirilli) have on the behaviour of model cellular pathways. Pathway wavefront shape, pathway concentration gradients, and chemical species distribution are measured in the three different shapes. We also quantify the impact of internal cellular clutter on the same pathways. Through this work we show that variations in the shape or configuration of these common cell shapes alter model cell behaviour.

  20. Modeling signalized intersection safety with corridor-level spatial correlations.

    Science.gov (United States)

    Guo, Feng; Wang, Xuesong; Abdel-Aty, Mohamed A

    2010-01-01

    Intersections in close spatial proximity along a corridor should be considered as correlated due to interacted traffic flows as well as similar road design and environmental characteristics. It is critical to incorporate this spatial correlation for assessing the true safety impacts of risk factors. In this paper, several Bayesian models were developed to model the crash data from 170 signalized intersections in the state of Florida. The safety impacts of risk factors such as geometric design features, traffic control, and traffic flow characteristics were evaluated. The Poisson and Negative Binomial Bayesian models with non-informative priors were fitted but the focus is to incorporate spatial correlations among intersections. Two alternative models were proposed to capture this correlation: (1) a mixed effect model in which the corridor-level correlation is incorporated through a corridor-specific random effect and (2) a conditional autoregressive model in which the magnitude of correlations is determined by spatial distances among intersections. The models were compared using the Deviance Information Criterion. The results indicate that the Poisson spatial model provides the best model fitting. Analysis of the posterior distributions of model parameters indicated that the size of intersection, the traffic conditions by turning movement, and the coordination of signal phase have significant impacts on intersection safety.

  1. Spatial Variations of PAH Properties in M17SW Revealed by Spitzer/IRS Spectral Mapping

    Science.gov (United States)

    Yamagishi, M.; Kaneda, H.; Ishihara, D.; Oyabu, S.; Suzuki, T.; Onaka, T.; Nagayama, T.; Umemoto, T.; Minamidani, T.; Nishimura, A.; Matsuo, M.; Fujita, S.; Tsuda, Y.; Kohno, M.; Ohashi, S.

    2016-12-01

    We present Spitzer/IRS mid-infrared spectral maps of the Galactic star-forming region M17 as well as IRSF/SIRIUS Brγ and Nobeyama 45 m/FOREST 13CO (J = 1-0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2 μm. We find that the PAH emission features are bright in the region between the H ii region traced by Brγ and the molecular cloud traced by 13CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially resolved Spitzer/IRS maps, we examine spatial variations of the PAH properties in detail. As a result, we find that the interband ratio of PAH 7.7 μm/PAH 11.3 μm varies locally near M17SW, but rather independently of the distance from the OB stars in M17, suggesting that the degree of PAH ionization is mainly controlled by local conditions rather than the global UV environments determined by the OB stars in M17. We also find that the interband ratios of the PAH 12.0 μm, 12.7 μm, 13.5 μm, and 14.2 μm features to the PAH 11.3 μm feature are high near the M17 center, which suggests structural changes of PAHs through processing due to intense UV radiation, producing abundant edgy irregular PAHs near the M17 center.

  2. Spatial variation in keystone effects: Small mammal diversity associated with black-tailed prairie dog colonies

    Science.gov (United States)

    Cully, J.F.; Collinge, S.K.; Van Nimwegen, R. E.; Ray, C.; Johnson, W.C.; Thiagarajan, B.; Conlin, D.B.; Holmes, B.E.

    2010-01-01

    Species with extensive geographic ranges may interact with different species assemblages at distant locations, with the result that the nature of the interactions may vary spatially. Black-tailed prairie dogs Cynomys ludovicianus occur from Canada to Mexico in grasslands of the western Great Plains of North America. Black-tailed prairie dogs alter vegetation and dig extensive burrow systems that alter grassland habitats for plants and other animal species. These alterations of habitat justify the descriptor " ecological engineer," and the resulting changes in species composition have earned them status as a keystone species. We examined the impact of black-tailed prairie dogs on small mammal assemblages by trapping at on- and off-colony locations at eight study areas across the species' geographic range. We posed 2 nested hypotheses: 1) prairie dogs function as a keystone species for other rodent species; and 2) the keystone role varies spatially. Assuming that it does, we asked what are the sources of the variation? Black-tailed prairie dogs consistently functioned as a keystone species in that there were strong statistically significant differences in community composition on versus off prairie dog colonies across the species range in prairie grassland. Small mammal species composition varied along both latitudinal and longitudinal gradients, and species richness varied from 4 to 11. Assemblages closer together were more similar; such correlations approximately doubled when including only on- or off-colony grids. Black-tailed prairie dogs had a significant effect on associated rodent assemblages that varied regionally, dependent upon the composition of the local rodent species pool. Over the range of the black-tailed prairie dog, on-colony rodent richness and evenness were less variable, and species composition was more consistent than off-colony assemblages. ?? 2010 The Authors.

  3. Spatial and temporal variation of water quality in the coastal lagoons of Sinaloa

    Science.gov (United States)

    Paez-Osuna, F.; Lopez-Aguiar, L. K.; Del Río-Chuljak, A.; Ruiz-Fernandez, A. C.

    2007-05-01

    The Mexican state of Sinaloa has 656 km of coastline and 221,600 ha of coastal lagoons, and is characterized by a high fishing and agriculture activity. It is well known that agricultural activities constitute a major factor affecting the water quality in the coastal waters. The current study focused on the 6 more important coastal lagoons of Sinaloa (Topolobampo-Ohuira-Santa María, Navachiste-San Ignacio-Macapule, Santa María-La Reforma, Altata-Ensenada del Pabellón, Ceuta and Teacapán-Agua Brava) with the aim to evaluate the water quality spatial and temporal variation at the lagoons (physico-chemical parameters, nutrients (N, P and Si), dissolved oxygen, total suspended solids and chlorophyll a) and to assess its eutrophication status. The water samples were collected in several stations at each lagoon (between 9 and 23 stations depending on the lagoon area) at low and high tides, during three different weather periods (dry-warm, rainy and dry-cold seasons) between May 2004 and April 2005. Mean concentrations of nutrients (μM), dissolved oxygen (mg/L) and chlorophyll a (mg/m3) obtained for each variable were comparable between lagoons (total N=51±45; total P= 2.5±1.5; Si=23±31; DO=6.7±1.8; Chll=1.7±1.9) although seasonal and spatial differences were observed at each lagoon. The nutrient concentrations measured fell in the typical concentration intervals for coastal lagoons; however, critical sampling points were identified and related to direct discharges of untreated effluents from municipal wastes, aquaculture farms and agriculture drain ditches.

  4. Spatial and temporal variation of CO over Alberta using measurements from satellite, aircrafts, and ground stations

    Science.gov (United States)

    Marey, H. S.; Hashisho, Z.; Fu, L.; Gille, J.

    2014-12-01

    Alberta is Canada's largest oil producer and its oil sand deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) are examined for the 12 year period from 2002-2013. Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations of forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009-December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons, summer and spring. Distinct seasonal patterns of CO at the urban site s (Edmonton and Calgary cities) point to the strong influence of traffic. Meteorological parameters play an important role on the CO spatial distribution at various pressure levels. Northern Alberta shows stronger upward lifting motion which leads to larger CO total column values while the poor dispersion in central and south Alberta exacerbates the surface CO pollution. Inter-annual variations of satellite data depict a slightly decreasing trend for both regions while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical

  5. Spatial and temporal variation in CO over Alberta using measurements from satellites, aircraft, and ground stations

    Science.gov (United States)

    Marey, H. S.; Hashisho, Z.; Fu, L.; Gille, J.

    2015-04-01

    Alberta is Canada's largest oil producer, and its oil sands deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) is examined for the 12-year period from 2002 to 2013. The Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations in forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009-December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons: summer and spring. Distinct seasonal patterns of CO at the urban sites (Edmonton and Calgary) point to the strong influence of traffic. Meteorological parameters play an important role in the CO spatial distribution at various pressure levels. Northern Alberta shows a stronger upward lifting motion which leads to larger CO total column values, while the poor dispersion in central and southern Alberta exacerbates the surface CO pollution. Interannual variations in satellite data depict a slightly decreasing trend for both regions, while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical

  6. Spatial and temporal variation in the canopy cover in a tropical semi-deciduous forest

    Directory of Open Access Journals (Sweden)

    Edmilson Bianchini

    2001-09-01

    Full Text Available This study was developed in the Mata dos Godoy State Park (23° 27’S, 51° 15’W South Brazil which present great environmental heterogeneity when its north portion (ridge is compared with the southern portion (valley, where there are some flooded areas. The forest formation is classified as tropical semi-deciduous forest. Spatial and temporal variations in the degree of the canopy cover were compared at flooded and unflooded sites. The measures were taken seasonally in 100m² plots using a spherical densiometer from spring 1995 to winter 1996. The flooded area was more open and lighter and had a greater spatial and temporal variation in the canopy cover than the unflooded areas. The greater heterogeneity in the flooded area could be due to structural characteristics of the canopy (greater spacing between individual trees, lower canopy and less stratified canopy, more frequent natural disturbances and a greater degree of deciduousness. These causes seemed to be related to the presence of the river and flooding.Este estudo foi desenvolvido no Parque Estadual Mata dos Godoy (23° 27’ S, 51° 15’ W, região Sul do Brasil. O Parque apresenta grande heterogeneidade ambiental quando as partes norte (espigão e sul (fundo de vale são comparadas. A floresta é classificada como tropical semi-decidual. As variações espaciais e temporais no grau de cobertura do dossel foram comparadas em sítios esporadicamente alagáveis e não alagáveis do Parque. Leituras foram realizadas sazonalmente, em parcelas de 100 m², com um densiômetro esférico, da primavera de 1995 até o inverno de 1996. A área alagável apresentou maior variação espacial e temporal na cobertura do dossel do que as áreas não alagáveis, indicando ser mais aberta e mais iluminada. Esta maior heterogeneidade da área alagável pode ser devido às características estruturais do dossel (maior espaçamento entre indivíduos arbóreos, dossel mais baixo e menos estratificado

  7. Spatial and temporal variation of CO over Alberta using measurements from satellite, aircrafts, and ground stations

    Directory of Open Access Journals (Sweden)

    H. S. Marey

    2014-12-01

    Full Text Available Alberta is Canada's largest oil producer and its oil sand deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO levels over Alberta. The multispectral product that uses both near-infrared (NIR and the thermal-infrared (TIR radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT are examined for the 12 year period from 2002–2013. Moderate Resolution Imaging Spectroradiometer (MODIS thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations of forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System aircraft CO profiles (April 2009–December 2011 are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons, summer and spring. Distinct seasonal patterns of CO at the urban site s (Edmonton and Calgary cities point to the strong influence of traffic. Meteorological parameters play an important role on the CO spatial distribution at various pressure levels. Northern Alberta shows stronger upward lifting motion which leads to larger CO total column values while the poor dispersion in central and south Alberta exacerbates the surface CO pollution. Inter-annual variations of satellite data depict a slightly decreasing trend for both regions while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO

  8. Temporal and spatial variations in road traffic noise for different frequency components in metropolitan Taichung, Taiwan.

    Science.gov (United States)

    Wang, Ven-Shing; Lo, Ei-Wen; Liang, Chih-Hsiang; Chao, Keh-Ping; Bao, Bo-Ying; Chang, Ta-Yuan

    2016-12-01

    Road traffic noise exposure has been associated with auditory and non-auditory health effects, but few studies report noise characteristics. This study determines 24-h noise levels and analyzes their frequency components to investigate associations between seasons, meteorology, land-use types, and traffic. We set up 50 monitoring stations covering ten different land-use types and conducted measurements at three times of the year to obtain 24-h-average A-weighted equivalent noise levels (LAeq,24h) and frequency analyses from 2013 to 2014 in Taichung, Taiwan. Information on land-use types, road parameters, traffic flow rates, and meteorological variables was also collected for analysis with the annual averages of road traffic noise and its frequency components. The annual average LAeq,24h in Taichung was 66.4 ± 4.7 A-weighed decibels (dBA). Significant differences in LAeq,24h and frequency components were observed between land-use types (all p-values traffic flow rates, and land-use types were significantly associated with annual average LAeq,24h (all p-values traffic (Spearman's coefficient = 0.795) and the highest prediction in the multiple linear regression (R(2) = 0.803; adjusted R(2) = 0.765). These findings reveal the spatial variation in road traffic noise exposure in Taichung. The highest correlation and predictive capacity was observed between this variation and noise levels at 125 Hz. We recommend that governmental agencies should take actions to reduce noise levels from traffic vehicles. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Near-surface remote sensing of spatial and temporal variation in canopy phenology.

    Science.gov (United States)

    Richardson, Andrew D; Braswell, Bobby H; Hollinger, David Y; Jenkins, Julian P; Ollinger, Scott V

    2009-09-01

    There is a need to document how plant phenology is responding to global change factors, particularly warming trends. "Near-surface" remote sensing, using radiometric instruments or imaging sensors, has great potential to improve phenological monitoring because automated observations can be made at high temporal frequency. Here we build on previous work and show how inexpensive, networked digital cameras ("webcams") can be used to document spatial and temporal variation in the spring and autumn phenology of forest canopies. We use two years of imagery from a deciduous, northern hardwood site, and one year of imagery from a coniferous, boreal transition site. A quantitative signal is obtained by splitting images into separate red, green, and blue color channels and calculating the relative brightness of each channel for "regions of interest" within each image. We put the observed phenological signal in context by relating it to seasonal patterns of gross primary productivity, inferred from eddy covariance measurements of surface-atmosphere CO2 exchange. We show that spring increases, and autumn decreases, in canopy greenness can be detected in both deciduous and coniferous stands. In deciduous stands, an autumn red peak is also observed. The timing and rate of spring development and autumn senescence varies across the canopy, with greater variability in autumn than spring. Interannual variation in phenology can be detected both visually and quantitatively; delayed spring onset in 2007 compared to 2006 is related to a prolonged cold spell from day 85 to day 110. This work lays the foundation for regional- to continental-scale camera-based monitoring of phenology at network observatory sites, e.g., National Ecological Observatory Network (NEON) or AmeriFlux.

  10. Spatial variation in background mortality among dominant coral taxa on Australia's Great Barrier Reef.

    Directory of Open Access Journals (Sweden)

    Chiara Pisapia

    Full Text Available Even in the absence of major disturbances (e.g., cyclones, bleaching, corals are consistently subject to high levels of background mortality, which undermines individual fitness and resilience of coral colonies. Partial mortality may impact coral response to climate change by reducing colony ability to recover between major acute stressors. This study quantified proportion of injured versus uninjured colonies (the prevalence of injuries and instantaneous measures of areal extent of injuries across individual colonies (the severity of injuries, in four common coral species along the Great Barrier Reef in Australia: massive Porites, encrusting Montipora, Acropora hyacinthus and Pocillopora damicornis. A total of 2,276 adult colonies were surveyed three latitudinal sectors, nine reefs and 27 sites along 1000 km2 on the Great Barrier Reef. The prevalence of injuries was very high, especially for Porites spp (91% and Montipora encrusting (85% and varied significantly, but most lay at small spatial scales (e.g., among colonies positioned <10-m apart. Similarly, severity of background partial mortality was surprisingly high (between 5% and 21% but varied greatly among colonies within the same site and habitat. This study suggests that intraspecific variation in partial mortality between adjacent colonies may be more important than variation between colonies in different latitudinal sectors or reefs. Differences in the prevalence and severity of background partial mortality have significant ramifications for coral capacity to cope with increasing acute disturbances, such as climate-induced coral bleaching. These data are important for understanding coral responses to increasing stressors, and in particular for predicting their capacity to recover between subsequent disturbances.

  11. Consequences of variations in spatial turbulence characteristics for fatigue life time of wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, G.C.

    1998-09-01

    The fatigue loading of turbines situated in complex terrain is investigated in order to determine the crucial parameters in the spatial structure of the turbulence in such situations. The parameter study is performed by means of numerical calculations, and it embraces three different wind turbine types, representing a pitch controlled concept, a stall controlled concept, and a stall controlled concept with an extremely flexible tower. For each of the turbine concepts, the fatigue load sensibility to the selected turbulence characteristics are investigated for three different mean wind speeds at hub height. The selected mean wind speeds represent the linear-, the stall-, and the post stall aerodynamic region for the stall controlled turbines and analogously the unregulated-, the partly regulated-, and the fully regulated regime for the pitch controlled turbine. Denoting the turbulence component in the mean wind direction by u, the lateral turbulence component by v, and the vertical turbulence component by w, the selected turbulence characteristics comprise the u-turbulence length scale, the ratio between the v- and w-turbulence intensities and the u-turbulence intensity, the uu-coherence decay factor, and finally the u-v and u-w cross-correlations. The turbulence length scale in the mean wind direction gives rise to significant modification of the fatigue loading on all the investigated wind turbine concepts, but for the other selected parameter variations, large individual differences exists between the turbines. With respect to sensitivity to the performed parameter variations, the Vestas V39 wind turbine is the most robust of the investigated turbines. The Nordtank 500/37 turbine, equipped with the (artificial) soft tower, is by far the most sensitive of the investigated turbine concepts - also much more sensitive than the conventional Nordtank 500/37 turbine equipped with a traditional tower. (au) 2 tabs., 43 ills., 7 refs.

  12. Water chemistry in Kuji river. Its spatial and seasonal variations in major ions and organic substances

    Energy Technology Data Exchange (ETDEWEB)

    Niina, Toshiaki; Matsunaga, Takeshi; Amano, Hikaru [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1996-02-01

    As a basic research with a aim to clarify the migration behavior of radionuclides in rivers, the characteristics of dissolved ions and organic substances in river water, which characteristics may affect the behavior, was investigated. The investigation was carried out for the Kuji river in the northern Kanto district (Japan) comprising four sampling campaigns in 1994 for 10 locations from the upstream to the downstream. Concentrations of major ions, iron and manganese species and organic substances were analyzed in laboratory. Values of temperature of the water, pH, conductivity, dissolved oxygen were measured in the field. This investigation was conducted mainly under low water flow conditions of the river, while a limited number of campaigns were under high flow conditions due to precipitation events. The concentrations of major inorganic ions increased steadily toward the down-stream, resulting in approximately two times increase for the traveling distance of 100 km. They showed a seasonal variation that they were highest in the spring and lowest in the autumn when there were most concentrated precipitation events in a year. The constituents were mainly Na{sup +}, Ca{sup 2+}, SO{sub 4}{sup 2-} and HCO{sub 3}{sup -}, and were similar for every sampling locations and seasons. Concentrations of dissolved organic substances (carbon compounds) were lowest in the upstream and increased about twice in the downstream as well as major inorganic ions. Their level was 1-3 mg/l, which can be ranked as relatively lower in general values for fresh water environments. They were highest in the spring (average over the locations: 2.2 mg/l) and lowest in the autumn (1.3 mg/l) and also in the winter (1.3 mg/l). These results will be useful as a basic understanding of spatial and seasonal variations of river water chemistry, especially related to the organic substances which can bind with radionuclides to make a mobile complex. (author).

  13. Spatial variation in the frequency-magnitude distribution of earthquakes under the tectonic framework in the Middle East

    Science.gov (United States)

    Mousavi, S. Mostafa

    2017-10-01

    Spatial variations of seismic energy released and b-value over the Middle East region are investigated based on a seismicity catalog from 1995 to 2007. The goal is to use these seismic parameters and based on other geodetic and geophysical observations, such as GPS measurements, strain rate model, fault distribution, focal mechanism, crustal model, Q model, and gravity measurements, etc., to uncover spatial patterns that seem anomalous. Areas of high energy released (cumulative) seem to correspond to the areas of relatively high b-values. Areas of high energy released and high b-values seem to correspond very well with the location of continental collision where earthquake activities are high. The divergent boundary between Arabia and African plates and subduction zone at Makran seem to correspond to low to moderate energy release. Northern Pamir, Azerbaijan-Caucasus, the lower part of Zagros Mountains, eastern Turkey, Owen Fracture Zone, Strait of Bob-el-Mandeb, and south of the Sulaiman Shear Zone seem to correspond to high cumulative energy-released, high strain rate, high b-values, and high fault density. While, the central and eastern Iran, southern Zagros, northern Pakistan, Gulf of Aden, Alborz, southwest of the Caspian Sea, western Caucasus and Kopeh-Dagh seem to correspond with lower b-values. The cross-section map for Hindu-Kush shows general decreasing of the b-values with depth, however, a region of high b-value is observed underneath Pamir at depths from 170 to 230 km. This anomaly region can be due to dehydration of Pamir crustal slab at depth.

  14. A spatial analysis of county-level variation in syphilis and gonorrhea in Guangdong Province, China.

    Directory of Open Access Journals (Sweden)

    Nicholas X Tan

    Full Text Available BACKGROUND: Sexually transmitted infections (STI have made a resurgence in many rapidly developing regions of southern China, but there is little understanding of the social changes that contribute to this spatial distribution of STI. This study examines county-level socio-demographic characteristics associated with syphilis and gonorrhea in Guangdong Province. METHODS/PRINCIPAL FINDINGS: This study uses linear regression and spatial lag regression to determine county-level (n = 97 socio-demographic characteristics associated with a greater burden of syphilis, gonorrhea, and a combined syphilis/gonorrhea index. Data were obtained from the 2005 China Population Census and published public health data. A range of socio-demographic variables including gross domestic product, the Gender Empowerment Measure, standard of living, education level, migrant population and employment are examined. Reported syphilis and gonorrhea cases are disproportionately clustered in the Pearl River Delta, the central region of Guangdong Province. A higher fraction of employed men among the adult population, higher fraction of divorced men among the adult population, and higher standard of living (based on water availability and people per room are significantly associated with higher STI cases across all three models. Gross domestic product and gender inequality measures are not significant predictors of reported STI in these models. CONCLUSIONS/SIGNIFICANCE: Although many ecological studies of STIs have found poverty to be associated with higher reported STI, this analysis found a greater number of reported syphilis cases in counties with a higher standard of living. Spatially targeted syphilis screening measures in regions with a higher standard of living may facilitate successful control efforts. This analysis also reinforces the importance of changing male sexual behaviors as part of a comprehensive response to syphilis control in China.

  15. Basic relations for the period variation models of variable stars

    OpenAIRE

    Mikulášek, Zdeněk; Gráf, Tomáš; Zejda, Miloslav; Zhu, Liying; Qian, Shen-Bang

    2012-01-01

    Models of period variations are basic tools for period analyzes of variable stars. We introduce phase function and instant period and formulate basic relations and equations among them. Some simple period models are also presented.

  16. Spatial and temporal CCN variations in convection-permitting aerosol microphysics simulations in an idealised marine tropical domain

    Science.gov (United States)

    Planche, Céline; Mann, Graham W.; Carslaw, Kenneth S.; Dalvi, Mohit; Marsham, John H.; Field, Paul R.

    2017-03-01

    A convection-permitting limited area model with periodic lateral boundary conditions and prognostic aerosol microphysics is applied to investigate how concentrations of cloud condensation nuclei (CCN) in the marine boundary layer are affected by high-resolution dynamical and thermodynamic fields. The high-resolution aerosol microphysics-dynamics model, which resolves differential particle growth and aerosol composition across the particle size range, is applied to a domain designed to match approximately a single grid square of a climate model. We find that, during strongly convective conditions with high wind-speed conditions, CCN concentrations vary by more than a f