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1.
The most generally used method for estimating the basin-wide sequence and scaling of first and last occurrences, based on their occurrence in local sections, is Shaw’s graphic correlation method. The key step in this method is the determination of the line of correlation (LOC), which represents the best estimate of the correlation between two local sections, or between a local section and a composite standard. In general, available techniques for fitting the LOC for multiple sections are tedious, subjective, or computationally expensive. A new method employing genetic algorithms can dramatically reduce the effort involved in determining the LOC and produces stable biostratigraphic correlations and composite range charts objectively and efficiently. Genetic algorithms are an artificial intelligence technique that excels in locating the optimum solution from a large number of alternative choices. In the case of the LOC, the alternative choices are the number of line segments comprising the complete line and the positions of each segment’s beginning and end points. For a given number of segments, a wide range of alternative LOCs can be rapidly evaluated and a potential optimum fit determined. It is also possible to estimate the point when no further refinement of the fit by adding line segments is necessary. Genetic algorithms can also be applied to other methods for quantitative biostratigraphy. 相似文献
2.
甘肃靖远石炭系纳缪尔阶高分辨率生物地层研究 总被引:1,自引:1,他引:0
依据对甘肃靖远纳缪尔阶的定量地层研究 ,介绍了图形对比法的基本原理和操作过程 ,建立了靖远石炭系纳缪尔阶生物地层复合标准 ,确定了剖面间的精确对比关系 ,提出了榆树梁剖面是该区发育最为齐全的剖面。榆树梁东沟剖面纳缪尔期地层与榆树梁剖面同期沉积相比 ,缺失了约 30 m厚的地层 ,大水沟剖面靖远组仅相当于榆树梁剖面靖远组中部。 相似文献
3.
Estimating the undiscovered mineral resources of a terrane is a challenging, yet essential, task in mineral exploration. We
apply Zipf’s law rank statistical analysis to estimate the undiscovered nickel sulphide resources in the Norseman-Wiluna Greenstone
Belt, Western Australia. The analysis suggests that about 3.0 to 10.0 Mt of nickel sulphide resources are yet to be discovered
in this belt, compared to the currently known total nickel sulphide endowment of 10.8 Mt. This undiscovered nickel sulphide
endowment is likely to be hosted by incompletely delineated deposits and undiscovered deposits in less explored komatiites
in the belt. Using the more detailed data subset of the Kambalda domain, this study manipulates Zipf’s law to estimate the
sizes of undiscovered deposits, in addition to the domain’s total nickel sulphide endowment estimate. Importantly, regression
analysis shows that the gradient of the line of best fit through the logarithmic rank-size plot for the detailed Kambalda
data subset is −1. This gradient, which is the key Zipf’s law constant k, has the value of −0.92 for the Norseman-Wiluna Greenstone Belt which is collectively less mature than the Kambalda domain.
This result corroborates the use of k = −1 in Zipf’s law predictive analyses of mineral resources for deposit populations for which the value of k = −1 has not yet been attained due to exploration immaturity. 相似文献
4.
Rosario Turvey 《GeoJournal》2006,67(3):207-222
Research on the practice of adopting local economic development (LED) strategies is important to understand our local world
as it is and what it might be made to be as a place for community. This article on economic development strategies (EDS) highlights
the results from a survey of 82 small communities representing the Yukon Territory and ten provinces in Canada. The purpose
was to evaluate the positive and additive effects of past local action and community initiatives so as to understand the variation
in the adoption of local economic development strategies of Canada’s small towns and local municipalities. Using a questionnaire
as instrument for data collection, the study employed hierarchical regression analysis and principal component analysis (PCA)
as method for factor extraction and composite assessment on the effects of adopting EDS for community. The PCA solution was
applied to evaluate the structure of correlation between the community characteristics as control variables in the baseline
model for regression analysis and the past local action and community initiatives as independent variables. The results of
the hierarchical regression analysis showed that local initiatives have significant and additive effects on the adoption of
EDS by small communities. The study findings offer some insights into some perspectives of ‘development from within’ to mean
the local economic development practice in Canadian communities. 相似文献
5.
V. B. Piip 《Moscow University Geology Bulletin》2009,64(5):296-305
The paper discusses the mantle structure along superlong seismic profiles in Russia examined using the method of homogenous
functions. Two-dimensional heterogeneous sections of the upper mantle were calculated from travel-time curves to a depth of
500–600 km with allowance for the Earth’s curvature without using any a priory information. The presentation of sections as
surfaces with a shaded relief combined with velocity contours allowed discerning the principal interfaces in the lithosphere
and in the upper mantle, the internal structure of layers, and local heterogeneities of different shapes (convective cells
and slabs) in the sections. 相似文献
6.
The match game: New stratigraphic correlation algorithms 总被引:1,自引:0,他引:1
New algorithms for automatic correlation of geologic strata are introduced. The algorithms are extensions of the Smith and Waterman (1980) dynamic programming technique and include several features that greatly increase the utility for sedimentary sequences. Gaps in correlation (unconformities) caused by local nondeposition or eroded strata can include in a single event several strata. Furthermore, these gaps can be weighted as a single event, rather than as the sum of gap events for each strata. In addition, one or several adjacent strata in a second column can be correlated (matched) with one or several strata in a second column. Deletions within one of these multiple matches are also possible. The new algorithms include the method of minimum distance and the method of maximum similarity. Within this context, a similarity algorithm is given to locate and correlate the best matching segments or intervals from each stratigraphic column. All correlations within a preset distance of the optimum likewise can be produced for any of these algorithms. An example of specific assignments of these weight functions is given for correlation of well logs from the San Juan Basin. 相似文献
7.
L. D. Akulenko Yu. G. Markov V. V. Perepelkin L. V. Rykhlova 《Astronomy Reports》2009,53(11):1070-1077
The fundamental astrometric problem of high-accuracy interpolation and forecasting of the Earth’s polar motion on short time
scales from 1–2 to 10–30 days is studied. Hierarchies of interval length and parameter accuracy are established using appropriate
models for the process. Filtering algorithms are adjusted using a weighted least squares fit of measurements of the International
Earth Rotation Service (IERS). Best-fit estimates for the main features of the motion are obtained for various time intervals;
interpolations and forecasts are compared with the IERS measurements. 相似文献
8.
This paper juxtaposes the actual areas of settlement and settlement activities of Chinese migrants in Brisbane’s southern
suburbs since the mid-1980s, with the concomitant, ‘government planned’ construction of the city’s Chinatown as an ‘exotic,’
‘ethnic,’ and ‘cosmopolitan’ landmark. It argues that while the latter, as with Chinatowns in other Australian and world cities,
has continued to appropriate the symbols of so-called ‘Chineseness’ to sell the locale to non-Chinese, the former, in recalling
the notion of ‘ethnoburbia,’ significantly evinces actual Chinese migrants’ agency and role in place-making. In the process,
these migrants have not only established a local, ethnically meaningful environment, but also challenged the still current
metonymic Western image of the Chinese as preferring life in ‘ethnic’ urban enclaves that had its origin from early Chinese
settlement and fundamentally detached from the lives of other ethnic groups per se. Indeed greater recognition and comprehension of such locales may go a long way to illustrate that many Chinese living in
Australia today do not fit the territorial, place-based identity often associated with them in the imagination of mainstream
society. 相似文献
9.
This study estimates the excess mortality attributable to excessive heat events (EHEs) for forty major U.S. cities during
1975–1995 and 1975–2004. We calculate these results using the spatial synoptic classification method to identify EHE days.
Step-wise regressions are then used to estimate the location-specific mortality algorithms that can account for the impact
of the EHEs’ duration, severity, and timing. Our excess mortality results are expressed both as lives lost and associated
mortality rates (excess deaths per 100,000 residents) using 2000 Census population estimates. Our results generally show a
reduction in EHE-attributable mortality rates since 1996. Adjusting our results to account for changes in the average number
of EHE days per year in each period does not affect this general conclusion. However, this adjustment has a considerable impact
on a measure of the cities’ relative performance in terms of reducing this EHE-attributable excess mortality. Our results
indicate there is promise for further reductions in EHE-attributable mortality from the approximately 1300 excess deaths per
summer we identify using data from the 1975–2004 period. However, the magnitude of this result highlights the significant
health burden of EHEs relative to other extreme weather events in the United States and suggests it is worthy of additional
attention. Our results also raise important questions with respect to evaluating the performance of EHE notification and response
programs and how EHE-attributable mortality should be estimated for future scenarios, notably for climate change projections. 相似文献
10.
Today, various types of fair trade systems propose new forms of relationships between producers and consumers. If several
studies have provided accurate understandings of consumers’ motivations to buy fair trade products, the specific kinds of
consumer involvement that are emphasized in those systems remain partly unknown. In France, controversies about the regulation
and organization of fair trade with producers from Southern countries has led to broader debates about how consumers can best
express their solidarity with producers. In these debates local food networks are often portrayed as good examples of fair
trade and as having potential to redefine the role of the consumer in the marketplace (or in commercial relations). Based
on examination of the type of mechanisms used to enrol consumers in local and fair trade networks, we have distinguished two
main kinds of consumers’ involvement. The first one may be called “delegation” and is based on market mechanisms. The second
one is called “empowerment” and is based on contractual mechanisms between consumers and producers and on the construction
of collective choices. This latter kind of consumer involvement points out the capacity of alternative food networks to empower
consumers in a more broadly political sense.
相似文献
Claire LamineEmail: |
11.
Image analysis of three-dimensional microtomographic image data has become an integral component of pore scale investigations
of multiphase flow through porous media. This study focuses on the validation of image analysis algorithms for identifying
phases and estimating porosity, saturation, solid surface area, and interfacial area between fluid phases from gray-scale
X-ray microtomographic image data. The data used in this study consisted of (1) a two-phase high precision bead pack from
which porosity and solid surface area estimates were obtained and (2) three-phase cylindrical capillary tubes of three different
radii, each containing an air–water interface, from which interfacial area was estimated. The image analysis algorithm employed
here combines an anisotropic diffusion filter to remove noise from the original gray-scale image data, a k-means cluster analysis
to obtain segmented data, and the construction of isosurfaces to estimate solid surface area and interfacial area. Our method
was compared with laboratory measurements, as well as estimates obtained from a number of other image analysis algorithms
presented in the literature. Porosity estimates for the two-phase bead pack were within 1.5% error of laboratory measurements
and agreed well with estimates obtained using an indicator kriging segmentation algorithm. Additionally, our method estimated
the solid surface area of the high precision beads within 10% of the laboratory measurements, whereas solid surface area estimates
obtained from voxel counting and two-point correlation functions overestimated the surface area by 20–40%. Interfacial area
estimates for the air–water menisci contained within the capillary tubes were obtained using our image analysis algorithm,
and using other image analysis algorithms, including voxel counting, two-point correlation functions, and the porous media
marching cubes. Our image analysis algorithm, and other algorithms based on marching cubes, resulted in errors ranging from
1% to 20% of the analytical interfacial area estimates, whereas voxel counting and two-point correlation functions overestimated
the analytical interfacial area by 20–40%. In addition, the sensitivity of the image analysis algorithms on the resolution
of the microtomographic image data was investigated, and the results indicated that there was little or no improvement in
the comparison with laboratory estimates for the resolutions and conditions tested. 相似文献
12.
Uma Shankar Kalachand Sain Michael Riedel 《Journal of the Geological Society of India》2012,79(2):199-209
The passive eastern Indian margin is rich in gas hydrates, as inferred from the wide-spread occurrences of bottom-simulating
reflectors (BSRs) and recovery of gas hydrate samples from various sites in the Krishna Godavari (KG) and Mahanadi (MN) basins
drilled by the Expedition 01 of the Indian National Gas Hydrate Program (NGHP). The BSRs are often interpreted to mark the
thermally controlled base of gas hydrate stability zone (BGHSZ). Most of the BSRs exhibit moderate to typically higher amplitudes
than those from other seismic reflectors. We estimate the average geothermal gradient of ∼40°C/km and heat flow varying from
23 to 62 mW/m2 in the study area utilizing the BSR’s observed on seismic sections. Further we provide the BGHSZ where the BSR is not continuous
or disturbed by local tectonics or hidden by sedimentation patterns parallel to the seafloor with a view to understand the
nature of BSR. 相似文献
13.
The properties of giant radio sources (GRS’s) are considered with the aim of identifying conditions contributing to their
formation, using data from the literature, the Sloan Digital Sky Survey (SDSS), and the APM catalog. The optical and radio
properties of normal-size radio sources, (≤1 Mpc), are compared. The following conclusions are reached. (1) The fraction of
objects with broad emission lines among GRS’s with high-excitation spectra is the same as for isotropic samples of radio sources;
in the framework of the “unified scheme,” this testifies to an isotropic distribution of angles between the radio jets of
GRS’s and the line of sight, i.e., GRS’s do not represent a population of objects whose radio jets are in the plane of the
sky. (2) Giant radio sources do not differ from normal radio sources in the distributions of various asymmetry parameters
for their extended radio components; in the unified scheme, the similarity of the asymmetry distributions for giant radio
galaxies and giant radio quasars suggests that the origin of the asymmetry of their extended radio components is inhomogeneity
of the external conditions. (3) The observed powers of the radio jets of giant and normal radio sources do not differ, making
it unlikely that the large sizes of the GRS’s are due to this factor. (4) The richness and character of the environments of
giant and normal radio sources do not differ: giant host galaxies are found in both isolated fields and in clusters of up
to Abell class 1 in richness. This argues against the idea that a low density of the environment is the only origin of GRS’s.
(5) The relatively large fraction of radio sources with two pairs of extended radio components (so-called double-double radio
sources) among GRS’s testifies that the lifetimes of GRS’s are approximately an order of magnitude longer than those of normal
radio sources.Given the equal spatial densities of nearby (z < 0.1) GRS’s and FR II radio sources with powers P
1.4 MHz > 1025 W/Hz, this indicates that ∼10% of FR II radio sources have lifetimes an order of magnitude longer, and evolve into GRS’s.
(6) The small (∼0.1) ratio of the number of known GRS’s to the number of normal FR II radio sources, together with the observed
spatial density of GRS’s at z ∼ 0.6, which is an order of magnitude lower than the predicted value, suggests that a considerable number of GRS’s were missed
by surveys at z > 0.1, possibly due to observational selection effects because of their relatively low radio powers and radio surface brightnesses.
(7) The absence of “double-double” giant quasars suggests that these objects have a shorter activity time scale than GRS’s.
In an evolutionary scenario that is an alternative to the unified scheme uniting “radio loud” quasars and radio galaxies,
radio quasars evolve with time into radio galaxies, and the observed relative number of radio quasars among the GRS’s (∼10%)
can be interpreted as reflecting the existence of a long-lived population of “radio loud” quasars comprising ∼10% of all radio
quasars, with such a population of long-lived radio quasars being the parent population for giant radio galaxies. 相似文献
14.
15.
The 2D modeling of clastic accumulation in clinoforms under marine conditions is performed. For this purpose, two algorithms are used: the first, “geometric” one implies that the shapes of sedimentary bodies are defined by geometric methods; the second is a “diffusion” method, which is based on numerical solution of the diffusion equation. Modeling of the test section is made using different versions of these algorithms. Comparative analysis of modeling results suggests that the best fit with real sections is achieved by a combination of the geometric and diffusion algorithms. 相似文献
16.
Some commonly used interpolation algorithms are analyzed briefly in this paper. Among all of the methods, biharmonic spline
interpolation, which is based on Green’s function and proposed by Sandwell, has become the mainstream method for its high
precision, simplicity and flexibility. However, the minimum curvature method has two flaws. First, it suffers from undesirable
oscillations between data points, which is solved by interpolation with splines in tension. Second, the computation time is
approximately proportional to the cube of the number of data constraints, making the method slow for situations with dense
data coverage. Focusing on the second problem, this paper introduces the moving surface spline interpolation method based
on Green’s function, and the interpolation error equations are deduced. Because the proposed method only chooses the nearest
data points by using the merge sort algorithm for interpolating, the computation time is greatly decreased. The optimal number
of the nearest points can be determined by using the interpolation error estimation equation. No matter how many data points
there are, this method can be implemented without difficulty. Examples show that the proposed method can obtain high interpolation
precision and high computation speed at the same time. 相似文献
17.
An interesting feature of recently published experimental data on high temperature deformation of Solnhofen limestone and Carrara marble is that it is not possible, for either rock, to fit isothermal points on a log strain-rate vs. log stress plot to a single straight line as required for a flow law of the familiar form e = Aexp(- H/RT)σn. Instead for Solnhofen limestone the data can be well fitted to two straight line segments suggesting a change from power law with high stress exponent (at high stress) to power law with low stress exponent at low stress. However, the constant strain-rate data are even better fitted by a single composite flow law formed by addition of the two power laws; a single flow law operates throughout but the strain-rate contributions of the two components change in response to changing stress. Published microstructural evidence supports this composite flow law approach.For Carrara marble constant data provides much poorer control and it is possible to propose several composite flow laws (formed by addition of two or three separate power-law components) all of which provide reasonable correspondence with the data. Stress relaxation data is then used both to test these flow models and to suggest others. Flow models that are broadly compatible with constant and stress relaxation data can then be tested against microstructural measurements.It is suggested that, by treating a set of composite flow laws as alternative hypotheses to be tested against all available data, a more realistic Theological model will result. Composite flow laws have the major advantage of being able to represent a smooth transition from one dominant deformation mechanism to another irrespective of how wide the transition zone may be. 相似文献
18.
Hakan Mete Dogan 《Journal of Earth System Science》2009,118(6):701-710
Utilizing remote sensing (RS) and geographic information systems (GIS) tools, mineral composite characteristics (ferrous minerals
(FM), iron oxide (IO), and clay minerals (CM)) of the Kelkit River Basin (15913.07 km2) in Turkey were investigated and mapped. Mineral composite (MC) index maps were produced from three LANDSAT-ETM+ satellite
images taken in 2000. Resulting MC index maps were summarized in nine classes by using ‘natural breaks’ classification method
in GIS. Employing bi-variety correlation analysis, relationships among index maps were investigated. According to the results,
FM and IO index maps showed positive correlation, while CM index map is negatively correlated with FM and IO index maps. Negative
correlations between iron and clay variables suggested that the dominant clay minerals of the study area might be smectite,
illite, kaolinite, and chlorite, which have little or no iron content. Using field data for which their geographic coordinates
had been determined by global positioning system (GPS), developed MC maps were verified, and found dependable for environmental
and ecological modeling studies. 相似文献
19.
Markov chain Monte Carlo methods for conditioning a permeability field to pressure data 总被引:3,自引:0,他引:3
Generating one realization of a random permeability field that is consistent with observed pressure data and a known variogram
model is not a difficult problem. If, however, one wants to investigate the uncertainty of reservior behavior, one must generate
a large number of realizations and ensure that the distribution of realizations properly reflects the uncertainty in reservoir
properties. The most widely used method for conditioning permeability fields to production data has been the method of simulated
annealing, in which practitioners attempt to minimize the difference between the ’ ’true and simulated production data, and
“true” and simulated variograms. Unfortunately, the meaning of the resulting realization is not clear and the method can be
extremely slow. In this paper, we present an alternative approach to generating realizations that are conditional to pressure
data, focusing on the distribution of realizations and on the efficiency of the method. Under certain conditions that can
be verified easily, the Markov chain Monte Carlo method is known to produce states whose frequencies of appearance correspond
to a given probability distribution, so we use this method to generate the realizations. To make the method more efficient,
we perturb the states in such a way that the variogram is satisfied automatically and the pressure data are approximately
matched at every step. These perturbations make use of sensitivity coefficients calculated from the reservoir simulator. 相似文献
20.
Manoj K. Pandit Helga de Wall Narendra K. Chauhan 《Journal of Earth System Science》2008,117(3):201-209
A number of fine-grained sericite bearing pelitic, schistose lithologies occur along the Archean (Banded Gneiss Complex)-Proterozoic
(Aravalli Supergroup) contact (APC) in the Udaipur valley in NW Indian craton. These Al-rich lithologies (subsequently metamorphosed)
have been described as ‘paleosols’, developed over a 3.3 Ga old Archean gneissic basement and are overlain by Paleoproterozoic
Aravalli quartzite. The paleosol was developed between 2.5 and 2.1, coincident with the globally recognized Great Oxidation
Event (GOE). In previous studies these paleosol sections were interpreted to have developed under reducing environment, however,
the finding of a ‘ferricrete’ zone in the upper part of Tulsi Namla section (east of Udaipur) during the present study (in
addition to earlier reported lithologies) has led to an alternative suggestion of oxygen-rich conditions during paleosol development.
The Tulsi Namla paleosol section shows all the features characteristic of a complete paleosol section described from other
Archean cratons. The paleosol includes sericite schist with kyanite as the prevalent Al-silicate in the lower part of profile
while chloritoid and Fe-oxides typify the Fe-rich upper part. Alumina has remained immobile during the weathering process
while Fe and Mn show a decrease in the lower part of the section and an abrupt rise in the upper part, in the ferricrete zone.
The field and geochemical data indicate that the Tulsi Namla section is an in situ weathering profile and at least the upper part shows evidence of oxidizing conditions. 相似文献