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261.
An iterative inverse method, the sequential self-calibration method, is developed for mapping spatial distribution of a hydraulic
conductivity field by conditioning on nonreactive tracer breakthrough curves. A streamline-based, semi-analytical simulator
is adopted to simulate solute transport in a heterogeneous aquifer. The simulation is used as the forward modeling step. In
this study, the hydraulic conductivity is assumed to be a deterministic or random variable. Within the framework of the streamline-based
simulator, the efficient semi-analytical method is used to calculate sensitivity coefficients of the solute concentration
with respect to the hydraulic conductivity variation. The calculated sensitivities account for spatial correlations between
the solute concentration and parameters. The performance of the inverse method is assessed by two synthetic tracer tests conducted
in an aquifer with a distinct spatial pattern of heterogeneity. The study results indicate that the developed iterative inverse
method is able to identify and reproduce the large-scale heterogeneity pattern of the aquifer given appropriate observation
wells in these synthetic cases. 相似文献
262.
The Tau Model for Data Redundancy and Information Combination in Earth Sciences: Theory and Application 总被引:3,自引:0,他引:3
Sunderrajan Krishnan 《Mathematical Geosciences》2008,40(6):705-727
Many decision-making processes in the Earth sciences require the combination of multiple data originating from diverse sources.
These data are often indirect and uncertain, and their combination would call for a probabilistic approach. These data are
also partially redundant with each other or with all others taken jointly. This overlap in information arises due to a variety
of reasons—because the data arises from the same geology, because they originate from the same location or the same measurement
device, etc. The proposed tau model combines partially redundant data, each taking the form of a prior probability for the
event being assessed to occur given that single datum. The parameters of that tau model measure the additional contribution
brought by any single datum over that of all previously considered data; they are data sequence-dependent and also data value-dependent.
Data redundancy depends on the sequence in which the data is considered and also on the data values themselves. However, for
a given sequence, averaging the tau model parameters over all possible data values leads to exact analytical expressions and
corresponding approximations and inference avenues. Information on multiple-point connectivity of permeability arrives from
core data, well-test data and seismic data which are defined over varying supports with complex redundancy between these information
sources. In order to compute these tau weights for determining connectivity, one needs a model of data redundancy, here expressed
as a vectorial training image (Ti) constructed using a prior conceptual knowledge of geology and the physics of data measurement.
From such a vectorial Ti, the tau weights can be computed exactly. Neglecting data redundancy leads to an over-compounding
of individual data information and the possible risk of making extreme decisions. 相似文献
263.
Fu-Ping Liu Rui-Zhong Li Jin-yao Li Hui-Guo Chen Chang-Chun Yang 《Mathematical Geosciences》2008,40(7):813-829
The group time delay (GTD) formulae of quasi-total reflection of inhomogeneous P-polarized electromagnetic waves (P-PEW, whose electric field parallels to the plane of incidence), caused by the Goos–Hänchen effect, is derived by the phase shift of the wave. A numerical example where the frequency equals to 1 GHz is given. The curves of calculating results show that there are three discontinuous points at the critical angle of phase shift vector, the critical angle of attenuation vector and 90○. When the angle of incidence is equal to one of these three angles, the GTD will become infinite, and the electromagnetic wave will propagate along the interface. The GTD will be very large, when the angle of incidence is close to one of these three angles. The results indicate that there is an important relationship between the two critical angles and the conductivity and permittivity of the two strata, and that the GTD has an important relationship with the angle of incidence. These results can be used to determine the lithology of the strata and to delimit the interfaces of strata more effectively. It is suggested that this research may prove useful in electromagnetic logging analysis and, perhaps, in the design of logging instruments. 相似文献
264.
Rorik A. Peterson 《Mathematical Geosciences》2008,40(3):277-298
Differential frost heave is often implicated in the formation of patterned ground in regions subject to recurrent freezing
and thawing. A linear stability analysis (LSA) indicates that a continuum model of frost heave is linearly unstable under
typical natural freezing conditions of silty-clay soils. A two-dimensional non-linear numerical analysis corroborates the
frozen time LSA results, and also indicates the importance of non-linear and time-dependent terms that ultimately lead to
a preferred mode, which the LSA fails to predict. Instability of the one-dimensional solution occurs at shallow freezing depths
and near-zero surface loads when positive perturbations in the ice content at the freezing front lead to a concomitant increase
in thermomolecular pressure and upward ice velocity. Differential frost heave can then occur because of the increased heat
flux from the perturbed surfaces. A three-dimensional model using random initial surface perturbations indicates that regular
surface patterns will evolve with a length scale in the order of 2–4 meters, which corresponds quite closely with naturally-occurring
non-sorted patterned ground. 相似文献
265.
Non-Linear Theory and Power-Law Models for Information Integration and Mineral Resources Quantitative Assessments 总被引:7,自引:0,他引:7
Qiuming Cheng 《Mathematical Geosciences》2008,40(5):503-532
Singular physical or chemical processes may result in anomalous amounts of energy release or mass accumulation that, generally,
are confined to narrow intervals in space or time. Singularity is a property of different types of non-linear natural processes
including cloud formation, rainfall, hurricanes, flooding, landslides, earthquakes, wildfires, and mineralization. The end
products of these non-linear processes can be modeled as fractals or multifractals. Hydrothermal processes in the Earth’s
crust can result in ore deposits characterized by high concentrations of metals with fractal or multifractal properties. Here
we show that the non-linear properties of the end products of singular mineralization processes can be applied for prediction
of undiscovered mineral deposits and for quantitative mineral resource assessment, whether for mineral exploration or for
regional, national and global planning for mineral resource utilization. In addition to the general theory and framework for
the non-linear mineral resources assessment, this paper focuses on several power-law models proposed for characterizing non-linear
properties of mineralization and for geoinformation extraction and integration. The theories, methods, and computer system
discussed in this paper were validated using a case study dealing with hydrothermal Au mineral potential in southern Nova
Scotia, Canada. 相似文献
266.
Inversely-Mapped Analytical Solutions for Flow Patterns around and within Inclined Elliptic Inclusions in Fluid-Saturated Rocks 总被引:1,自引:0,他引:1
Chongbin Zhao Bruce E. Hobbs Alison Ord Shenglin Peng Liangming Liu 《Mathematical Geosciences》2008,40(2):179-197
In this paper, an inverse mapping is used to transform the previously-derived analytical solutions from a local elliptical
coordinate system into a conventional Cartesian coordinate system. This enables a complete set of exact analytical solutions
to be derived rigorously for the pore-fluid velocity, stream function, and excess pore-fluid pressure around and within buried
inclined elliptic inclusions in pore-fluid-saturated porous rocks. To maximize the application range of the derived analytical
solutions, the focal distance of an ellipse is used to represent the size of the ellipse, while the length ratio of the long
axis to the short one is used to represent the geometrical shape of the ellipse. Since the present analytical solutions are
expressed in a conventional Cartesian coordinate system, it is convenient to investigate, both qualitatively and quantitatively,
the distribution patterns of the pore-fluid flow and excess pressure around and within many different families of buried inclined
elliptic inclusions. The major advantage in using the present analytical solution is that they can be conveniently computed
in a global Cartesian coordinate system, which is widely used in many scientific and engineering computations. As an application
example, the present analytical solutions have been used to investigate how the dip angle of an inclined elliptic inclusion
affects the distribution patterns of the pore-fluid flow and excess pore-fluid pressure when the permeability ratio of the
elliptic inclusion is of finite but nonzero values. 相似文献
267.
杨山晚古生代沉积盆地成因类型及其与桐柏-大别造山带关系的探讨 总被引:16,自引:1,他引:15
杨山晚古生代沉积盆地位于桐柏-大别山北麓,它具有明显的前陆盆地沉积特点,由早期(D2?—C1)的复理石建造到晚期(C1—P?)的磨拉石建造;古生物地理分析表明其与华北、扬子陆块都有密不可分的联系,其间不可能有古洋盆的存在,因而它应当是桐柏一大别造山带碰撞造山过程中形成的前陆盆地。杨山晚古生代前陆盆地的形成说明,扬子陆块和华北陆块的陆-陆碰撞起始于晚泥盆世之前(S3—D2),而桐柏-大别造山带中生代的构造事件则可能代表一次大规模陆内逆冲-推覆作用。 相似文献
268.
扬子地台前寒武纪-寒武纪界线地层的微体植物化石群 总被引:10,自引:2,他引:8
前寒武纪一寒武纪界线地层在扬子地台发育良好、分布广泛,并有包括微体植物群、海藻、瓶形原生物、具硬体动物及‘澄江动物群’等化石的发现。因而,扬子地台成为研究前寒武纪-寒武纪界线生物地层的代表地区之一。基于对扬子地台前寒武纪-寒武纪界线地层已知微体植物化石记录的回顾和论定,总结概括了下寒武统微体植物化石组合:寒武系最底部硅质磷块岩中的Micrhystridium-Paracymatiosphaera-Megathrix组合和较高层位页岩的Skiagia-Annulum-Archaeodiscina组合。它们分别与Anabarites-Circotheca-Protohertzina小壳动物化石带和Parabadiella及Eoredlichia三叶虫带相对应。与东欧地台疑源类生物地层相对照,扬子地台Micrhystridium-Paracymatiosphaera-Megathrix组合的纵向分布大体和东欧地台Asteridiumtornatum-Comasphaeridiumvelvetum组合带相一致,而以上两地台的化石组合产出层位可能都略高于纽芬兰东部剖面,依据Phycodespedum所厘定的寒武系底界? 相似文献
269.
本文记述了发现于辽南复州湾上石炭统太原组的燕海扇类,计5属17种。讨论了Annuliconcha与Paradoxipecten的属征及有关问题。上述发现在东北地区尚属首次。 相似文献
270.
An experimental study of magnesium-isotope fractionation in chlorophyll-a photosynthesis 总被引:2,自引:0,他引:2
Measurements are presented of the magnesium isotopic composition of chlorophyll-a, extracted from cyanobacteria, relative to the isotopic composition of the culture medium in which the cyanobacteria were grown. Yields of 50-93% chlorophyll-a were achieved from the pigment extracts of Synechococcus elongatus, a unicellular cyanobacteria. This material was then digested using concentrated nitric acid to extract magnesium. Separation was accomplished using columns of cation-exchange resin, which achieved a 103 ± 10% yield of magnesium from chlorophyll-a. This procedure ensured accurate measurement of the magnesium-isotopic ratios without isobaric interferences using a multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). We find a slight depletion in the heavier isotopes of magnesium in chlorophyll-a relative to culture medium, early growth phase: Δ26Mg = −0.71(±0.35)‰ and Δ25Mg = −0.37(±0.18)‰; late growth phase: Δ26Mg = −0.53(±0.20)‰ and Δ25Mg = −0.26(±0.11)‰, due to an apparent mass-dependent fractionation. We suggest that the small fractionation results from chelation during intracellular processes. A likely candidate for this chelation step involves the magnesium-chelatase enzyme, which mediates the insertion of magnesium to the tetrapyrrole ring during chlorophyll-a biosynthesis. Proof of this hypothesis can be tested with biological controls whereby steps in the enzymatic pathways of chlorophyll synthesis are selectively suppressed. 相似文献