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21.
22.
Zoltán Wéber 《Geophysical Journal International》2006,165(2):607-621
23.
24.
Daniel G. Brown Rick Riolo Derek T. Robinson Michael North William Rand 《Journal of Geographical Systems》2005,7(1):25-47
The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, we identify four key relationships affecting how geographic data (fields and objects) and agent-based process models can interact: identity, causal, temporal and topological. We discuss approaches to implementing tight integration, focusing on a middleware approach that links existing GIS and ABM development platforms, and illustrate the need and approaches with example agent-based models. 相似文献
25.
R. Pail 《Journal of Geodesy》2005,79(4-5):231-241
In the recent design of the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission, the gravity gradients are defined in the gradiometer reference frame (GRF), which deviates from the actual flight direction (local orbit reference frame, LORF) by up to 3–4°. The main objective of this paper is to investigate the effect of uncertainties in the knowledge of the gradiometer orientation due to attitude reconstitution errors on the gravity field solution. In the framework of several numerical simulations, which are based on a realistic mission configuration, different scenarios are investigated, to provide the accuracy requirements of the orientation information. It turns out that orientation errors have to be seriously considered, because they may represent a significant error component of the gravity field solution. While in a realistic mission scenario (colored gradiometer noise) the gravity field solutions are quite insensitive to small orientation biases, random noise applied to the attitude information can have a considerable impact on the accuracy of the resolved gravity field models. 相似文献
26.
Trevor Quinn A.-Xing Zhu James E. Burt 《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):324-338
Hydro-ecological modelers often use spatial variation of soil information derived from conventional soil surveys in simulation of hydro-ecological processes over watersheds at mesoscale (10–100 km2). Conventional soil surveys are not designed to provide the same level of spatial detail as terrain and vegetation inputs derived from digital terrain analysis and remote sensing techniques. Soil property layers derived from conventional soil surveys are often incompatible with detailed terrain and remotely sensed data due to their difference in scales. The objective of this research is to examine the effect of scale incompatibility between soil information and the detailed digital terrain data and remotely sensed information by comparing simulations of watershed processes based on the conventional soil map and those simulations based on detailed soil information across different simulation scales. The detailed soil spatial information was derived using a GIS (geographical information system), expert knowledge, and fuzzy logic based predictive mapping approach (Soil Land Inference Model, SoLIM). The Regional Hydro-Ecological Simulation System (RHESSys) is used to simulate two watershed processes: net photosynthesis and stream flow. The difference between simulation based on the conventional soil map and that based on the detailed predictive soil map at a given simulation scale is perceived to be the effect of scale incompatibility between conventional soil data and the rest of the (more detailed) data layers at that scale. Two modeling approaches were taken in this study: the lumped parameter approach and the distributed parameter approach. The results over two small watersheds indicate that the effect does not necessarily always increase or decrease as the simulation scale becomes finer or coarser. For a given watershed there seems to be a fixed scale at which the effect is consistently low for the simulated processes with both the lumped parameter approach and the distributed parameter approach. 相似文献
27.
离散裂隙渗流方法与裂隙化渗透介质建模 总被引:4,自引:1,他引:4
流体渗流模拟的连续介质方法通常适用于多孔地质体,并不一定适用于裂隙岩体,由于裂隙分布及其特征与孔隙差异较大。若流体渗流主要受裂隙的控制,对于一定尺寸的裂隙岩体,多孔介质假设则较难刻划裂隙岩体的渗流特征。离散裂隙渗流方法不但可直接用于模拟裂隙岩体非均质性和各向异性等渗流特征,而且可用其确定所研究的裂隙岩体典型单元体及其水力传导(渗透)张量大小。主要讨论了以下问题:(1)饱和裂隙介质中一般的离散流体渗流模拟;(2)裂隙岩体中的REV(典型单元体)及其水力传导(渗透)张量的确定;(3)利用离散裂隙网络流体渗流模型研究裂隙方向几何参数对水力传导系数和REV的影响;(4)在二维和三维离散裂隙流体渗流模型中对区域大裂隙和局部小裂隙的处理方法。调查结果显示离散裂隙流体渗流数学模型可用来评价不同尺度上的裂隙岩体的水力特征,以及裂隙方向对裂隙化岩体的水力特征有着不可忽视的影响。同时,局部小裂隙、区域大裂隙应当区别对待,以便据其所起的作用及水力特征,建立裂隙化岩体相应的流体渗流模型。 相似文献
28.
Groundwater-flow modeling in the Yucatan karstic aquifer, Mexico 总被引:1,自引:0,他引:1
Roger González-Herrera Ismael Sánchez-y-Pinto José Gamboa-Vargas 《Hydrogeology Journal》2002,10(5):539-552
The current conceptual model of the unconfined karstic aquifer in the Yucatan Peninsula, Mexico, is that a fresh-water lens
floats above denser saline water that penetrates more than 40 km inland. The transmissivity of the aquifer is very high so
the hydraulic gradient is very low, ranging from 7–10 mm/km through most of the northern part of the peninsula. The computer
modeling program AQUIFER was used to investigate the regional groundwater flow in the aquifer. The karstified zone was modeled
using the assumption that it acts hydraulically similar to a granular, porous medium. As part of the calibration, the following
hypotheses were tested: (1) karstic features play an important role in the groundwater-flow system; (2) a ring or belt of
sinkholes in the area is a manifestation of a zone of high transmissivity that facilitates the channeling of groundwater toward
the Gulf of Mexico; and (3) the geologic features in the southern part of Yucatan influence the groundwater-flow system. The
model shows that the Sierrita de Ticul fault, in the southwestern part of the study area, acts as a flow barrier and head
values decline toward the northeast. The modeling also shows that the regional flow-system dynamics have not been altered
despite the large number of pumping wells because the volume of water pumped is small compared with the volume of recharge,
and the well-developed karst system of the region has a very high hydraulic conductivity.
Electronic Publication 相似文献
29.
Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high level of shear resistance at large shear strain excursions. This pattern of response, known as a form of cyclic mobility, has been documented by a large body of laboratory sample tests and centrifuge experiments. A plasticity-based constitutive model is developed with emphasis on simulating the cyclic mobility response mechanism and associated pattern of shear strain accumulation. This constitutive model is incorporated into a two-phase (solid–fluid), fully coupled finite element code. Calibration of the constitutive model is described, based on a unique set of laboratory triaxial tests (monotonic and cyclic) and dynamic centrifuge experiments. In this experimental series, Nevada sand at a relative density of about 40% is employed. The calibration effort focused on reproducing the salient characteristics of dynamic site response as dictated by the cyclic mobility mechanism. Finally, using the calibrated model, a numerical simulation is conducted to highlight the effect of excitation frequency content on post-liquefaction ground deformations. 相似文献
30.
Chen Po-fang 《地震学报(英文版)》2002,15(5):519-525
To improve the accuracy of the numerical evaluation through the 3-D finite difference method, the surface boundary conditions
are added to modify the old program. The author has tested the new program by making calculations for the model constructed
by Wanamaker, et al (1984). The comparison between the numerical results obtained from this paper and those by Wannamaker, et al (1984) indicates that a pronounced improvement is realized in the evaluation of the horizontal magnetic components. Moreover,
better calculations for the vertical magnetic components are also obtainable by using the new program. 相似文献