Introduction: A symposium on Global Shadows: Africa in the Neoliberal World Order     

Alex Jeffrey  Colin McFarlane  Alexander Vasudevan 《Singapore journal of tropical geography》2008,29(3):251-253

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Parametric model for capacity curves     

Luis G. Pujades  Yeudy F. Vargas-Alzate  Alex H. Barbat  José R. González-Drigo 《Bulletin of Earthquake Engineering》2015,13(5):1347-1376

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Erratum to: Assessment of coastal communities’ vulnerability to floods using indicator-based approach: a case study of Greater Accra Metropolitan Area,Ghana     

Paul William Kojo Yankson  Alex Barimah Owusu  George Owusu  John Boakye-Danquah  Jacob Doku Tetteh 《Natural Hazards》2017,85(2):691-707

In this paper, the extent to which the potentially transit-dependent portion of the population is vulnerable to the effects of a hurricane is estimated. The vulnerability of an area is defined as a composite measure of the proportion of disadvantaged persons, distance to transit, and flooding potential of people within an area. Unlike past studies which have focused on the vulnerability of the population in relatively large geographic areas, this study estimates the vulnerability of the population in 30 m × 30 m areas as defined in the National Land Cover Database. Population estimates from the national census at block level are disaggregated to the 30 m × 30 m units using a modified dasymetric mapping method in ArcGIS. The modified mapping method assigns population to each small areal unit using weights estimated by regressing the area of each land use in a census block against the population in that block. The coefficients in the regression analysis are “weights” associating population with each land use, and are used to distribute the population in each census block to the small geographic units based on their land use. In a case study of New Orleans, the results show that some areas are not well served by the existing transit pickup locations, as evidenced by their high vulnerability scores. Reassignment of pickup point locations to cover higher vulnerability score areas was investigated using integer linear programming. The results show that the optimally located pickup points serve areas with a larger average vulnerability score than the current pickup points in the study area. The method appears to be helpful in identifying vulnerable areas that, subsequently, could receive improved hurricane evacuation service in the future.  相似文献   

Spatiotemporal analysis of residential flood exposure in the Atlanta,Georgia metropolitan area     

Ferguson  Alex P.  Ashley  Walker S. 《Natural Hazards》2017,87(2):989-1016

Natural Hazards - This research examines changes in residential built-environment flood exposure within the current boundaries of the Atlanta, Georgia metropolitan statistical area, by estimating...  相似文献   

Multiple Point Metrics to Assess Categorical Variable Models     

Jeff B. Boisvert  Michael J. Pyrcz  Clayton V. Deutsch 《Natural Resources Research》2010,19(3):165-175

Geostatistical models should be checked to ensure consistency with conditioning data and statistical inputs. These are minimum acceptance criteria. Often the first and second-order statistics such as the histogram and variogram of simulated geological realizations are compared to the input parameters to check the reasonableness of the simulation implementation. Assessing the reproduction of statistics beyond second-order is often not considered because the “correct” higher order statistics are rarely known. With multiple point simulation (MPS) geostatistical methods, practitioners are now explicitly modeling higher-order statistics taken from a training image (TI). This article explores methods for extending minimum acceptance criteria to multiple point statistical comparisons between geostatistical realizations made with MPS algorithms and the associated TI. The intent is to assess how well the geostatistical models have reproduced the input statistics of the TI; akin to assessing the histogram and variogram reproduction in traditional semivariogram-based geostatistics. A number of metrics are presented to compare the input multiple point statistics of the TI with the statistics of the geostatistical realizations. These metrics are (1) first and second-order statistics, (2) trends, (3) the multiscale histogram, (4) the multiple point density function, and (5) the missing bins in the multiple point density function. A case study using MPS realizations is presented to demonstrate the proposed metrics; however, the metrics are not limited to specific MPS realizations. Comparisons could be made between any reference numerical analogue model and any simulated categorical variable model.  相似文献   

Probabilistic data integration for characterization of spatial distribution of residual LNAPL     

Amir H. Hosseini  Clayton V. Deutsch  Kevin W. Biggar  Carl A. Mendoza 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(5):735-749

The spatial distribution of residual light non-aqueous phase liquid (LNAPL) is an important factor in reactive solute transport modeling studies. There is great uncertainty associated with both the areal limits of LNAPL source zones and smaller scale variability within the areal limits. A statistical approach is proposed to construct a probabilistic model for the spatial distribution of residual NAPL and it is applied to a site characterized by ultra-violet-induced-cone-penetration testing (CPT–UVIF). The uncertainty in areal limits is explicitly addressed by a novel distance function (DF) approach. In modeling the small-scale variability within the areal limits, the CPT–UVIF data are used as primary source of information, while soil texture and distance to water table are treated as secondary data. Two widely used geostatistical techniques are applied for the data integration, namely sequential indicator simulation with locally varying means (SIS–LVM) and Bayesian updating (BU). A close match between the calibrated uncertainty band (UB) and the target probabilities shows the performance of the proposed DF technique in characterization of uncertainty in the areal limits. A cross-validation study also shows that the integration of the secondary data sources substantially improves the prediction of contaminated and uncontaminated locations and that the SIS–LVM algorithm gives a more accurate prediction of residual NAPL contamination. The proposed DF approach is useful in modeling the areal limits of the non-stationary continuous or categorical random variables, and in providing a prior probability map for source zone sizes to be used in Monte Carlo simulations of contaminant transport or Monte Carlo type inverse modeling studies.  相似文献   

Climate change and the oceans – What does the future hold?     

Jelle Bijma  Hans-O. Pörtner  Chris Yesson  Alex D. Rogers 《Marine pollution bulletin》2013

The ocean has been shielding the earth from the worst effects of rapid climate change by absorbing excess carbon dioxide from the atmosphere. This absorption of CO₂ is driving the ocean along the pH gradient towards more acidic conditions. At the same time ocean warming is having pronounced impacts on the composition, structure and functions of marine ecosystems. Warming, freshening (in some areas) and associated stratification are driving a trend in ocean deoxygenation, which is being enhanced in parts of the coastal zone by upwelling of hypoxic deep water. The combined impact of warming, acidification and deoxygenation are already having a dramatic effect on the flora and fauna of the oceans with significant changes in distribution of populations, and decline of sensitive species. In many cases, the impacts of warming, acidification and deoxygenation are increased by the effects of other human impacts, such as pollution, eutrophication and overfishing.  相似文献   

Mode coupling analysis and differential rotation in a flow driven by a precessing cylindrical container     

Thierry Lehner  Waleed Mouhali  Jacques Leorat  Alex Mahalov 《地球物理与天体物理流体动力学》2013,107(4):369-401

We present a theoretical weakly nonlinear analysis of the dynamics of an inviscid flow submitted to both rotation and precession of an unbounded cylindrical container, by considering the coupling of two Kelvin (inertial) waves. The parametric centrifugal instability known for this system is shown to saturate when one expands the Navier–Stokes equation to higher order in the assumed small precession parameter (ratio of precession to rotation frequencies) with the derivation of two coupled Landau equations suitable to describe the dynamics of the modes. It is shown that an azimuthal mean flow with differential rotation is generated by this modes coupling. The time evolution of the associated dynamical system is studied. These theoretical results can be compared with water experiments and also to some numerical simulations where viscosity and finite length effects cannot be neglected.  相似文献   

A model of secondary upwelling over the shelf break     

Hezi Gildor  Erick Fredj  Alex Kostinski 《地球物理与天体物理流体动力学》2013,107(4):301-308

Motivated by our puzzling high-resolution radar observations of surface vortices in the nearly rectangular Gulf of Eilat/Aqaba, northern Red Sea, we propose and explore the driven cavity approach to this geophysical phenomenon. While the lid-driven cavity has long been considered a benchmark problem in computational fluid dynamics, its oceanographic context has not been considered. Despite the additional effects of rotation and stratification, our modeling demonstrates that when the fluid within a cavity geometrically similar to the Gulf of Eilat is driven by the external current, an interior vortex can develop as in our observations. Furthermore, the Eilat vortices appear only under relatively calm conditions, adding evidence to the intriguing possibility of their simple shear-driven origin.  相似文献   

Monitoring ground surface deformation over the North China Plain using coherent ALOS PALSAR differential interferograms     

Kui Zhang  Linlin Ge  Xiaojing Li  Alex Hay-Man Ng 《Journal of Geodesy》2013,87(3):253-265

North China Plain (Huabei Plain) is one of the most densely populated regions on earth. Due to excessive underground water extraction, the North China Plain has been experiencing severe ground deformation over the last three decades. Therefore, for the purpose of hazard mitigation, it is necessary to monitor the ground displacement occurred in this region. As an extension of the differential radar interferometry (DInSAR) technique, advanced DInSAR techniques involving multiple images have demonstrated the potential to effectively map ground displacement. Such techniques are able to measure the temporal evolution of ground deformation with millimetre-level accuracy by using a stack of differential interferograms. In this study, the ALOS PALSAR data acquired over the North China Plain, which cover an area of approximately 16,000 km $^2$ , were processed based on the concept of advanced DInSAR techniques. Because of the large size of the PALSAR images, a targeted processing strategy was designed. This strategy is able to reduce required disk storage space and I/O operations, leading to the improvement of the computational efficiency. The resulting mean deformation velocity map demonstrates that a large portion of the area covered by the data was affected by various degrees of ground deformation between January 2007 and April 2010. The ground deformation is mostly distributed in rural areas, while the downtown areas are generally stable.  相似文献