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91.
Singh et al (2005) examined the potential of the ANN and neuro-fuzzy systems application for the prediction of dynamic constant of rockmass.
However, the model proposed by them has some drawbacks according to fuzzy logic principles. This discussion will focus on
the main fuzzy logic principles which authors and potential readers should take into consideration. 相似文献
92.
The summer monsoon season of the year 2006 was highlighted by an unprecedented number of monsoon lows over the central and
the western parts of India, particularly giving widespread rainfall over Gujarat and Rajasthan. Ahmedabad had received 540.2mm
of rainfall in the month of August 2006 against the climatological mean of 219.8mm. The two spells of very heavy rainfall
of 108.4mm and 97.7mm were recorded on 8 and 12 August 2006 respectively. Due to meteorological complexities involved in replicating
the rainfall occurrences over a region, the Weather Research and Forecast (WRF-ARW version) modeling system with two different
cumulus schemes in a nested configuration is chosen for simulating these events. The spatial distributions of large-scale
circulation and moisture fields have been simulated reasonably well in this model, though there are some spatial biases in
the simulated rainfall pattern. The rainfall amount over Ahmedabad has been underestimated by both the cumulus parameterization
schemes. The quantitative validation of the simulated rainfall is done by calculating the categorical skill scores like frequency
bias, threat scores (TS) and equitable threat scores (ETS). In this case the KF scheme has outperformed the GD scheme for
the low precipitation threshold. 相似文献
93.
Natural radioactivity in sediment of Wei River,China 总被引:1,自引:0,他引:1
The concentrations of natural radionuclides in sediment of Wei River of China were measured using γ-ray spectrometry with
the aim of estimating the radiation hazard as establishing a database for radioactivity levels of river sediment of China.
The activity concentrations of 226Ra, 232Th and 40K in sediment samples ranged from 10.4 to 39.9 Bq kg−1, 15.3 to 54.8 Bq kg−1 and 514.8 to 1,175.5 Bq kg−1, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities
of Chinese soil and Shaanxi soil. Radium equivalent activity (Raeq), external hazard index (H
ex) and representative level index (I
γr) were calculated for the samples to assess the radiation hazards arising due to the use of these sediment samples in the
construction of dwellings. All the sediment samples have Raeq lower than the limit of 370 Bq kg−1, H
ex less than unity and I
γr close to 1 Bq kg−1. The overall mean outdoor terrestrial gamma dose rate is 64.8 nGy h−1 and the corresponding outdoor annual effective dose is 0.079 mSv. None of the studied location is considered a radiological
risk and sediment can be safely used in construction. 相似文献
94.
Quick-look assessments to identify optimal CO2 EOR storage sites 总被引:1,自引:0,他引:1
Vanessa Núñez-López Mark H. Holtz Derek J. Wood William A. Ambrose Susan D. Hovorka 《Environmental Geology》2008,54(8):1695-1706
A newly developed, multistage quick-look methodology allows for the efficient screening of an unmanageably large number of
reservoirs to generate a workable set of sites that closely match the requirements for optimal CO2 enhanced oil recovery (EOR) storage. The objective of the study is to quickly identify miscible CO2 EOR candidates in areas that contain thousands of reservoirs and to estimate additional oil recovery and sequestration capacities
of selected top options through dimensionless modeling and reservoir characterization. Quick-look assessments indicate that
the CO2 EOR resource potential along the US Gulf Coast is 4.7 billion barrels, and CO2 sequestration capacity is 2.6 billion metric tons. In the first stage, oil reservoirs are screened and ranked in terms of
technical and practical feasibility for miscible CO2 EOR. The second stage provides quick estimates of CO2 EOR potential and sequestration capacities. In the third stage, a dimensionless group model is applied to a selected set
of sites to improve the estimates of oil recovery and storage potential using appropriate inputs for rock and fluid properties,
disregarding reservoir architecture and sweep design. The fourth stage validates and refines the results by simulating flow
in a model that describes the internal architecture and fluid distribution in the reservoir. The stated approach both saves
time and allows more resources to be applied to the best candidate sites. 相似文献
95.
Curtis M. Oldenburg 《Environmental Geology》2008,54(8):1687-1694
A screening and ranking framework (SRF) has been developed to evaluate potential geologic carbon dioxide (CO2) storage sites on the basis of health, safety, and environmental (HSE) risk arising from CO2 leakage. The approach is based on the assumption that CO2 leakage risk is dependent on three basic characteristics of a geologic CO2 storage site: (1) the potential for primary containment by the target formation; (2) the potential for secondary containment
if the primary formation leaks; and (3) the potential for attenuation and dispersion of leaking CO2 if the primary formation leaks and secondary containment fails. The framework is implemented in a spreadsheet in which users
enter numerical scores representing expert opinions or published information along with estimates of uncertainty. Applications
to three sites in California demonstrate the approach. Refinements and extensions are possible through the use of more detailed
data or model results in place of property proxies. 相似文献
96.
The shallow water wave simulation model-SWAN incorporated with a simple fine sediment erosion model is applied to Hangzhou
Bay, China, to model the horizontal distribution of the maximum bottom orbital velocity and corresponding fine sediment erosion
rates induced by: (1) southeasterly steady winds (5, 20 and 30 m/s), (2) southwesterly steady winds (5 and 20 m/s); (3) northwesterly
steady winds (5 and 20 m/s); (4) east-southeasterly steady winds (5 and 20 m/s); (5) easterly steady winds (5 and 20 m/s)
under closed and unclosed boundaries; and (6) unsteady winds during the slack water periods. Results suggest: (1) the steady
wind wave-induced maximum bottom orbital velocities and corresponding fine sediment erosion rates generally increased with
the increasing steady winds; (2) closed and unclosed boundary conditions had more significant influences on modeled fine sediment
erosion rates under 5 m/s easterly steady winds than 20 m/s; and (3) steady and unsteady wind wave-induced maximum bottom
currents could be significant in eroding fine sediment bed in Hangzhou Bay. The results show implications for geomorphology,
sedimentology, coastal erosion, and environmental pollution mitigation in Hangzhou Bay. 相似文献
97.
98.
Yuan-Bao Wu Shan Gao Hong-Fei Zhang Sai-Hong Yang Wen-Fang Jiao Yong-Sheng Liu Hong-Lin Yuan 《Contributions to Mineralogy and Petrology》2008,155(1):123-133
The Hong’an area (western Dabie Mountains) is the westernmost terrane in the Qinling-Dabie-Sulu orogen that preserves UHP
eclogites. The ages of the UHP metamorphism have not been well constrained, and thus hinder our understanding of the tectonic
evolution of this area. LA-ICPMS U–Pb age, trace element and Hf isotope compositions of zircons of a granitic gneiss and an
eclogite from the Xinxian UHP unit in the Hong’an area were analyzed to constrain the age of the UHP metamorphism. Most zircons
are unzoned or show sector zoning. They have low trace element concentrations, without significant negative Eu anomalies.
These metamorphic zircons can be further subdivided into two groups according to their U–Pb ages, and trace element and Lu–Hf
isotope compositions. One group with an average age of 239 ± 2 Ma show relatively high and variable HREE contents (527 ≥ LuN ≥ 14) and 176Lu/177Hf ratios (0.00008–0.000931), indicating their growth prior to a great deal of garnet growth in the late stage of continental
subduction. The other group yields an average age of 227 ± 2 Ma, and shows consistent low HREE contents and 176Lu/177Hf ratios, suggesting their growth with concurrent garnet crystallization and/or recrystallization. These two groups of age
are taken as recording the time of prograde HP to UHP and retrograde UHP–HP stages, respectively. A few cores have high Th/U
ratios, high trace element contents, and a clear negative Eu anomaly. These features support a magmatic origin of these zircon
cores. The upper intercept ages of 771 ± 86 and 752 ± 70 Ma for the granitic gneiss and eclogite, respectively, indicate that
their protoliths probably formed as a bimodal suite in rifting zones in the northern margin of the Yangtze Block. Young Hf
model ages (T
DM1) of magmatic cores indicate juvenile (mantle-derived) materials were involved in their protolith formation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
99.
David M. Hirsch 《Contributions to Mineralogy and Petrology》2008,155(4):401-415
Garnet-bearing schists from the Waterville Formation of south-central Maine provide an opportunity to examine the factors
governing porphyroblast size over a range of metamorphic grade. Three-dimensional sizes and locations for all garnet porphyroblasts
were determined for three samples along the metamorphic field gradient spanning lowest garnet through sillimanite grade, using
high-resolution X-ray computed tomography. Comparison of crystal size distributions to previous data sets obtained by stereological
methods for the same samples reveals significant differences in mode, mean, and shape of the distributions. Quantitative textural
analysis shows that the garnets in each rock crystallized in a diffusion-controlled nucleation and growth regime. In contrast
to the typical observation of a correlation between porphyroblast size and position along a metamorphic field gradient, porphyroblast
size of the lowest-grade specimen is intermediate between the high- and middle-grade specimens’ sizes. Mean porphyroblast
size does not correlate with peak temperatures from garnet-biotite Fe-Mg exchange thermometry, nor is post-crystallization
annealing (Ostwald Ripening) required to produce the observed textures, as was previously proposed for these rocks. Robust
pseudosection calculations fail to reproduce the observed garnet core compositions for two specimens, suggesting that these
calc-pelites experienced metasomatism. For each of these two specimens, Monte Carlo calculations suggest potential pre-metasomatism
bulk compositions that replicate garnet core compositions. Pseudosection analyses allow the estimation of the critical temperatures
for garnet growth: ∼481, ∼477, and ∼485°C for the lowest-garnet-zone, middle-garnet-zone, and sillimanite-zone specimens,
respectively. Porphyroblast size appears to be determined in this case by a combination of the heating rate during garnet
crystallization, the critical temperature for the garnet-forming reaction and the kinetics of nucleation. Numerical simulations
of thermally accelerated, diffusion-controlled nucleation, and growth for the three samples closely match measured crystal
size distributions. These observations and simulations suggest that previous hypotheses linking the garnet size primarily
to the temperature at the onset of porphyroblast nucleation can only partially explain the observed textures. Also important
in determining porphyroblast size are the heating rate and the distribution of favorable nucleation sites. 相似文献
100.
Atomistic simulations have been carried out to investigate the mechanisms of noble gas incorporation in minerals using both the traditional two-region approach and the “supercell” method. The traditional two-region approach has been used to calculate defect energies for Ne, Ar, Kr and Xe incorporation in MgO, CaO, diopside and forsterite in the static limit and at one atmosphere pressure. The possibilities of noble gas incorporation via both substitution and interstitial mechanisms are studied. The favored mechanism varies from mineral to mineral and from noble gas to noble gas. In all minerals studied, the variation of the solution energies of noble gas substitution with atomic radius appears approximately parabolic, analogous to those for 1+, 2+, 3+ and 4+ trace element incorporation on crystal lattice sites. Noble gas solution energies thus also fall on a curve, similar to those previously observed for cations with different charges, but with much lower curvature.The “supercell” method has been used to investigate the pressure dependence of noble gas incorporation in the same systems. Results indicate a large variation of the solubility of the larger noble gases, Kr and Xe with pressure. In addition, explicit simulation of incorporation at the (0 0 1) surface of MgO shows that the solubility of the heavier noble gases may be considerably enhanced by the presence of interfaces. 相似文献