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991.
Ivar Aavatsmark 《Computational Geosciences》2007,11(3):199-206
Control-volume formulations for elliptic equations often use two-point flux stencils, even for skew grids. Any two-point flux
stencil may be interpreted as a multipoint flux stencil. This yields a definition of the permeability (or conductivity) tensor.
Formulas for calculating the permeability tensor, based on the user-specified quantities in the two-point flux stencil, are
given. Numerical test examples demonstrate the validity of the derivation.
相似文献
992.
Boris Kostic M. Peter Süss Thomas Aigner 《International Journal of Earth Sciences》2007,96(4):743-767
Quaternary sands and gravels form important, yet often highly heterogeneous economic deposits. Detailed 3-D analysis of the
sedimentary structure and stratigraphy of these deposits allows for an accurate estimation of exploitable material. This paper
presents a case study in SW Germany reconstructing the 3-D distribution of glacial sediments based on a high-resolution, process-orientated
sedimentary facies classification and lithostratigraphy integrated within the geo-modelling package gOcad. Situated along
the maximal ice-extent of the Rhine glacier during the last glaciation, the study area is characterised by a morphologically
prominent terminal moraine and its associated sandur, which form the stratigraphically youngest sediments of a glacial basin,
partially exposed in two gravel pits. These outcrops helped to reconstruct the complex sedimentary architecture of the northern
part of the glacial basin. The regional analysis is based on core data, as well as geoelectric and geomagnetic surveys. All
data were integrated into km-scale, high-resolution geological 3-D models, depicting the large-scale dynamics of multiple
glacier advances and retreats during the Early to Late Pleistocene. These models allow quantifying the thickness and volume
distribution of exploitable sandy gravel and help to evaluate the occurrence of non-exploitable interbedded diamicton horizons.
The high quality and quantity of gravels particularly north of the terminal moraine classifies the investigated area as very
prospective for raw materials exploitation in the future. 相似文献
993.
The ionospheric effect is one of the major errors in GPS data processing over long baselines. As a dispersive medium, it is
possible to compute its influence on the GPS signal with the ionosphere-free linear combination of L1 and L2 observables,
requiring dual-frequency receivers. In the case of single-frequency receivers, ionospheric effects are either neglected or
reduced by using a model. In this paper, an alternative for single-frequency users is proposed. It involves multiresolution
analysis (MRA) using a wavelet analysis of the double-difference observations to remove the short- and medium-scale ionosphere
variations and disturbances, as well as some minor tropospheric effects. Experiments were carried out over three baseline
lengths from 50 to 450 km, and the results provided by the proposed method were better than those from dual-frequency receivers.
The horizontal root mean square was of about 0.28 m (1σ). 相似文献
994.
995.
ZHANG Yi YAN Li 《地球空间信息科学学报》2007,10(4):276-281
A scheme for an automatic road surface modeling from a noisy point cloud is presented. The normal vectors of the point cloud are estimated by distance-weighted fitting of local plane. Then, an automati... 相似文献
996.
CHEN Luyao YUE Jianwei JIANG Weiguo LI Jing CHEN Yunhao 《地球空间信息科学学报》2007,10(4):299-302
The unceasing change problem of land information systems can be resolved through the refactoring and design pattern. To promote the implementation of design pattern and refactoring methods in developin... 相似文献
997.
998.
999.
In order to predict wind loading on trees (canopy height h) in partially harvested forests, it is necessary to characterize air flow and momentum transfer in progressively more complex
patterns where groups of trees (or aggregates) are retained. In this study, we used large-eddy simulation to explore the effects
of aggregate size, inter-aggregate spacing, and the ratio between the aggregate size and inter-aggregate spacing on air flow
and momentum transfer. Forty-five grid points across an aggregate were needed to achieve an adequate level of turbulence.
Using grid sizes of h/15 throughout was too viscous for the smaller aggregates. Vertical and horizontal flow deflection by the leading aggregates
sheltered some of the downstream aggregates to varying degrees where turbulence increased for subsequent rows. The number
of rows of protected aggregates decreased as aggregate dimensions and the space between aggregates increased. A theoretical
treatment of time-dependent wind is presented for the lead aggregate and a simulation case is presented for the case of a
gust of reduced wind passing through the aggregate pattern. The leading aggregate responded with decreasing moment for decreasing
ambient wind speed as predicted by theory. However, downwind aggregates experienced substantial increases in bending moment.
The overall results of the disruptive aspects of time dependence agrees with arguments regarding the role of irrotational
(potential) flow to this problem. Our treatment of retention pattern design is only a first step and further research suggestions
are presented. 相似文献
1000.
Smita Sirohi 《Climatic change》2007,84(1):91-110
India is perceived to be one of the most attractive Non-Annex I countries for CDM project development. There are more than
350 projects in the CDM pipeline, largely in the areas of renewable energy, energy efficiency in industries and fossil fuel
switching. This paper examines the socio-economic component of sustainable development commitments of the CDM projects to
see if they can make any impact on rural poverty in India, since the goal of poverty alleviation lies at the core of the country’s
development priorities. The study concludes that CDM is not contributing to rural poverty alleviation to any notable extent.
Nearly all the projects have a business orientation and are not directed to the development of rural poor. Even the renewable
energy projects will have limited role in up-liftment of the masses below poverty line due to their weak resource base. For
CDM to emerge as a “win–win” strategy for poverty alleviation projects should be aimed at the rural communities and designed
to accelerate agricultural growth in the rainfed regions of the country. 相似文献