Hybrid Gaussian-cubic radial basis functions for scattered data interpolation     

Pankaj K. Mishra  Sankar K. Nath  Mrinal K. Sen  Gregory E. Fasshauer 《Computational Geosciences》2018,22(5):1203-1218

Scattered data interpolation schemes using kriging and radial basis functions (RBFs) have the advantage of being meshless and dimensional independent; however, for the datasets having insufficient observations, RBFs have the advantage over geostatistical methods as the latter requires variogram study and statistical expertise. Moreover, RBFs can be used for scattered data interpolation with very good convergence, which makes them desirable for shape function interpolation in meshless methods for numerical solution of partial differential equations. For interpolation of large datasets, however, RBFs in their usual form, lead to solving an ill-conditioned system of equations, for which, a small error in the data can cause a significantly large error in the interpolated solution. In order to reduce this limitation, we propose a hybrid kernel by using the conventional Gaussian and a shape parameter independent cubic kernel. Global particle swarm optimization method has been used to analyze the optimal values of the shape parameter as well as the weight coefficients controlling the Gaussian and the cubic part in the hybridization. Through a series of numerical tests, we demonstrate that such hybridization stabilizes the interpolation scheme by yielding a far superior implementation compared to those obtained by using only the Gaussian or cubic kernels. The proposed kernel maintains the accuracy and stability at small shape parameter as well as relatively large degrees of freedom, which exhibit its potential for scattered data interpolation and intrigues its application in global as well as local meshless methods for numerical solution of PDEs.  相似文献   

Integration of stress testing with graph theory to assess the resilience of urban road networks under seismic hazards     

Nazli Yonca Aydin  H. Sebnem Duzgun  Friedemann Wenzel  Hans Rudolf Heinimann 《Natural Hazards》2018,91(1):37-68

Transportation networks daily provide accessibility and crucial services to societies. However, they must also maintain an acceptable level of service to critical infrastructures in the case of disruptions, especially during natural disasters. We have developed a method for assessing the resilience of transportation network topology when exposed to environmental hazards. This approach integrates graph theory with stress testing methodology and involves five basic steps: (1) establishment of a scenario set that covers a range of seismic damage potential in the network, (2) assessment of resilience using various graph-based metrics, (3) topology-based simulations, (4) evaluation of changes in graph-based metrics, and (5) examination of resilience in terms of spatial distribution of critical nodes and the entire network topology. Our case study was from the city of Kathmandu in Nepal, where the earthquake on April 25, 2015, followed by a major aftershock on May 12, 2015, led to numerous casualties and caused significant damage. Therefore, it is a good example for demonstrating and validating the developed methodology. The results presented here indicate that the proposed approach is quite efficient and accurate in assisting stakeholders when evaluating the resilience of transportation networks based on their topology.  相似文献   

Geologic hazards of the Ocoña river valley,Peru and the influence of small-scale mining     

Santi  P.  Manning  J.  Zhou  W.  Meza  P.  Colque  P. 《Natural Hazards》2021,108(3):2679-2700

Natural Hazards - The Ocoña River Valley, in the Arequipa Department in southern Peru, extends over 150 km from the Pacific coast to its headwaters in the Andes Mountains. While...  相似文献   

Evolution of bacterial communities in the Gironde Estuary (France) according to a salinity gradient     

《Estuarine, Coastal and Shelf Science》1987,24(1):95-108

Three surveys were performed in the Gironde Estuary (France) in August 1981, March 1982 and July 1982. For each campaign, seventy samples were taken by helicopter, in order to follow the tide along the estuary. Of the parameters that were studied, salinity appeared to be the most important and which controls the bacterial communities along the estuary. This paper deals with the evolution of bacterial communities along a salinity gradient. The information obtained from various bacteriological parameters (total bacterial counts, viable counts on salted and unsalted media, functional evenness) were convergent. The bacterial community is dominated by an halotolerant microflora. In the estuary, a continental microflora is followed by a marine microflora. The succession zone between these two microflora is located between 5 and 10‰ areas of salinity.  相似文献   

Coal exploration,mine planning and development: by Roy D. Merrit. Noyes Publication,Park Ridge,NJ, USA, 1986, 464 pages,U.S. $ 64.00     

《International Journal of Coal Geology》1988,9(4):399-400

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Temporal changes in pCFC-12 ages and AOU along two hydrographic sections in the eastern subtropical North Pacific     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(1):169-187

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Measurements of superoxide radical concentration and decay kinetics in the Gulf of Alaska     

S. Paul Hansard  Andrew W. Vermilyea  Bettina M. Voelker 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(9):1111-1119

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Geometry and architectural associations of co-genetic debrite–turbidite beds in basin-margin strata, Carboniferous Ross Sandstone (Ireland): Applications to reservoirs located on the margins of structurally confined submarine fans     

David R. Pyles  D.C. Jennette 《Marine and Petroleum Geology》2009,26(10):1974-1996

Co-genetic debrite–turbidite beds are most commonly found in distal basin-plain settings and basin margins. This study documents the geometry, architectural association and paleogeographic occurrence of co-genetic debrite–turbidite beds in the Carboniferous Ross Sandstone with the goal of reducing uncertainty in the interpretation of subsurface data in similarly shaped basins where oil and gas is produced.The Ross Sandstone of western Ireland was deposited in a structurally confined submarine basin. Two outcrops contain co-genetic debrite–turbidite beds: Ballybunnion and Inishcorker. Both of the exposures contain strata deposited on the margin of the basin. An integrated dataset was used to characterize the stratigraphy of the Ballybunnion exposure. The exposure is divided into lower, middle, and upper units. The lower unit contains laminated shale with phosphate nodules, structureless siltstone, convolute bedding/slumps, locally contorted shale, and siltstone turbidites. The middle unit contains co-genetic debrite–turbidite beds, siltstone turbidites, and structureless siltstone. Each co-genetic debrite–turbidite bed contains evidence that fluid turbulence and matrix strength operated alternately and possibly simultaneously during deposition by a single sediment-gravity-flow event. The upper unit contains thin-bedded sandy turbidites, amalgamated sandy turbidites, siltstone turbidites, structureless siltstone, and laminated shale. A similar vertical facies pattern is found at Inishcorker.Co-genetic debrite–turbidite beds are only found at the basin-margin. We interpret these distinct beds to have originated as sand-rich, fully turbulent flows that eroded muddy strata on the slope as well as interbedded sandstone and mudstone in axial positions of the basin floor forming channels and associated megaflute erosional surfaces. This erosion caused the axially dispersing flows to laterally evolve to silt- and clay-rich flows suspended by both fluid turbulence and matrix strength due to a relative increase in clay proportions and associated turbulence suppression. The flows were efficient enough to bypass the basin center/floor, physically disconnecting their deposits from coeval lobes, resulting in deposition of co-genetic debrite–turbidite beds on the basin margin. The record of these bypassing flows in axial positions of the basin is erosional surfaces draped by thin siltstone beds with organic debris.A detailed cross-section through the Ross Sandstone reveals a wedge of low net-to-gross, poor reservoir-quality strata that physically separates sandy, basin-floor strata from the basin margin. The wedge of strata is referred to as the transition zone. The transition zone is composed of co-genetic debrite–turbidite beds, structureless siltstone, slumps, locally contorted shale, and laminated shale. Using data from the Ross Sandstone, two equations are defined that predict the size and shape of the transition zone. The equations use three variables (thickness of basin-margin strata, thickness of coeval strata on the basin floor, and angle of the basin margin) to solve for width (w) and trajectory of the basinward side of the low net-to-gross wedge (β). Beta is not a time line, but a facies boundary that separates sandy basin floor strata from silty basin-margin strata. The transition zone is interpreted to exist on lateral and distal margins of the structurally confined basin.Seismic examples from Gulf of Mexico minibasins reveal a wedge of low continuity, low amplitude seismic facies adjacent to the basin margin. Strata in this wedge are interpreted as transition-zone sediments, similar to those in the Ross Sandstone. Besides defining the size and shape of the transition zone, the variables “w” and “β” define two important drilling parameters. The variable “w” corresponds to the minimum distance a well bore should be positioned from the lateral basin margin to intersect sandy strata, and “β” corresponds to the deviation (from horizontal) of the well bore to follow the interface between sandy and low net-to-gross strata. Calculations reveal that “w” and “β” are related to the relative amount of draping, condensed strata on the margin and the angle of the basin margin. Basins with shallowly dipping margins and relatively high proportions of draping, clay-rich strata have wider transition zones compared to basins with steeply dipping margins with little draping strata. These concepts can reduce uncertainty when interpreting subsurface data in other structurally confined basins including those in Gulf of Mexico, offshore West Africa, and Brunei.  相似文献   

A multiscale finite element formulation for axisymmetric elastoplasticity with volumetric locking     

Kaiming Xia  Kenn K. Q. Zhang 《国际地质力学数值与分析法杂志》2010,34(10):1076-1100

Similar to plane strain, axisymmetric stress problem is also highly kinematics constrained. Standard displacement‐based finite element exhibits volumetric locking issue in simulating nearly/fully incompressible material or isochoric plasticity under axisymmetric loading conditions, which severely underestimates the deformation and overestimates the bearing capacity for structural/geotechnical engineering problems. The aim of this paper is to apply variational multiscale method to produce a stabilized mixed displacement–pressure formulation, which can effectively alleviate the volumetric locking issue for axisymmetric stress problem. Both nearly incompressible elasticity and isochoric J₂ elastoplasticity are investigated. First‐order 3‐node triangular and 4‐node quadrilateral elements are tested for locking issues. Several representative simulations are provided to demonstrate the performance of the linear elements, which include the convergence study and comparison with closed‐form solutions. A comparative study with pressure Laplacian stabilized formulation is also presented. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Soft rock pillars     

J. F. Abel Jr. 《Geotechnical and Geological Engineering》1988,6(3):215-248

Summary Soft rock pillars can be designed by several methods available in the mining literature. All of these methods include the effect of shape, or geometry, on the average strength of specimens and pillars. All of the pillar design methods include some measurement of the strength of specimens of the pillar rock. The most common rock specimen strength property measured is the unconfined compressive strength. However, the average strength of triaxially confined rock specimens is much greater than the unconfined specimen strength, which can be more important to pillar strength. The estimation of the strength of a pillar is complicated by the decrease in rock specimen strength with increase in specimen size.Editor's note: In common with North American engineering practise, the paper uses English units throughout, where feasible conversions are included in the text. Where not, the following factors may be used: 1 inch=25.4 mm; 1 ft=0.3048 m; 1 lbf/in.^–2=6.895 kn/m^–2; 1Tonf.=8.896 kN.  相似文献