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251.
Lithospheric mantle signatures as revealed by zircon Hf isotopes of Late Triassic post‐collisional plutons from the central Korean peninsula,and their tectonic implications 下载免费PDF全文
Chang‐Sik Cheong Namhoon Kim Hui Je Jo Moonsup Cho Sung Hi Choi Hongying Zhou Jian‐zhen Geng 《地学学报》2015,27(2):97-105
The Mesozoic tectonic architecture of the Korean peninsula is largely governed by the continental collision between the North and South China blocks. Zircon Hf isotopic compositions presented in this study and whole‐rock geochemical and Sr‐Nd isotope data in the literature collectively suggest that the lithophile‐elements‐enriched signature of the Late Triassic post‐collisional plutons from the Gyeonggi massif in central Korea is a primary feature inherited from the metasomatized mantle lithosphere. Highly negative zircon εHf (t) values (?23 to ?19) of plutons from the middle and eastern parts of the massif indicate an ancient metasomatism of their mantle source. Distinctly higher zircon εHf (t) values (?15 to ?12) from the southwestern plutons are ascribed to a contribution from an accreted component of the South China‐like block. The involvement of asthenospheric mantle is not recognized in zircons from either group. The implications of these isotopic features are discussed in the context of Mesozoic collisional tectonics. 相似文献
252.
Mechanical properties of methane hydrate‐bearing soils are complex. Their behavior undergoes a significant change when hydrates dissociate and become methane gas. On the other hand, methane hydrates are ice‐like compounds and, depending on the hydrate accumulation habits and the degree of hydrate saturation, may cement soil particles into stronger and stiffer soils. A new constitutive model is proposed that is capable of capturing essential characteristics of hydrate‐bearing soils. The core of the model includes the spatial mobilized plane concept; a transformed stress, tij; the critical state; and the subloading framework. The proposed model gives soil responses due to stress changes or hydrate saturation changes or both. The performance of the model has been found satisfactory, over a range of hydrate saturation and confining pressures, using triaxial test data from laboratory‐synthesized samples and from field samples extracted from Nankai Trough, Japan. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
253.
Spatio‐temporal distribution of actual evapotranspiration in the Indus Basin Irrigation System 下载免费PDF全文
Strategic planning of optimal water use requires an accurate assessment of actual evapotranspiration (ETa) to understand the environmental and hydrological processes of the world's largest contiguous irrigation networks, including the Indus Basin Irrigation System (IBIS) in Pakistan. The Surface Energy Balance System (SEBS) has been used successfully for accurate estimations of ETa in different river basins throughout the world. In this study, we examined the application of SEBS using publically available remote sensing data to assess spatial variations in water consumption and to map water stress from daily to annual scales in the IBIS. Ground‐based ETa was calculated by the advection‐aridity method, from nine meteorological sites, and used to evaluate the intra‐annual seasonality in the hydrological year 2009–2010. In comparison with the advection‐aridity, SEBS computed daily ETa was slightly underestimated with a bias of ?0.15 mm day?1 during the kharif (wet; April–September) season, and it was overestimated with a bias of 0.23 mm day?1 in the rabi (dry; October–March) season. Monthly values of the ETa estimated by SEBS were significantly (P < 0.05) controlled by mean air temperature and rainfall, among other climatological variables (relative humidity, sunshine hours and wind speed). Because of the seasonal (kharif and rabi) differences in the water and energy budget in the huge canal command areas of the IBIS, ETa and rainfall were positively correlated in the kharif season and were negatively correlated during the rabi season. In addition, analysis of the evaporation process showed that mixed‐cropping and rice–wheat dominated areas had lower and higher water consumption rates, respectively, in comparison with other cropping systems in the basin. Basin areas under water stress were identified by means of spatial variations in the relative evapotranspiration, which had an average value of 0.59 and 0.42 during the kharif and the rabi seasons, respectively. The hydrological parameters used in this study provide useful information for understanding hydrological processes at different spatial and temporal scales. Results of this study further suggest that the SEBS is useful for evaluation of water resources in semi‐arid to arid regions over longer periods, if the data inputs are carefully handled. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
254.
Jung Hae Choi Katsuyuki Kawamura Kazushi Kimoto Yasuaki Ichikawa Byung‐Gon Chae 《国际地质力学数值与分析法杂志》2014,38(16):1744-1760
In porous media, chemical species that dissolve in pore water can be transported via diffusion mechanisms or advective fluxes, close to or far away from where precipitation occurs. In the case of a high‐level radioactive waste disposal system, compacted bentonite is used in a buffer material in an engineering barrier system to minimize the amount of specific nuclides that breach into the surrounding host rock. To minimize breaching, it is very important to understand the transport mechanism of multiple chemical species in porous media. In the following research, we introduced FEM analysis methods using the results of the molecular dynamics simulation and homogenization analysis (MD/HA) method. First, the diffusion coefficients of ions (Cl?, I?, and Na+) in different water layers of Na‐beidellite were calculated using the MD/HA procedure under various dry density (1.2, 1.6, and 2.0 Mg/m3) and temperature (293, 323, and 363 K) conditions. Next, using FEM analysis that used the MD/HA results as input parameters, the diffusion behaviors of ions in porous media were calculated. The results indicate that the diffusion coefficients of the interlayer water in Na‐beidellite are different from the diffusion coefficients under dry density conditions. Further, the concentration profiles (Ct/C0) of iodine and chloride are proportional to temperature but inversely proportional to dry density. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
255.
Differences in atmospheric and oceanic environments which affect the tropical cyclone (TC) activity between the late twenty-first century (2071?C2100, A1B) and the late twentieth century (1971?C2000, 20C3M) are analyzed using multi-model ensemble from 15 general circulation models. Six factors (vertical wind shear, 700?hPa relative humidity, 850?hPa relative vorticity, outgoing longwave radiation, precipitation, and sea surface temperature) related to TC genesis predicts that more TCs in the future will occur than in the present. The result of maximum potential intensity analysis shows the frequency of occurrence and influence of stronger TCs will increase over the western North Pacific in the future. Anomalous northerly in the mid-latitudes of East Asia due to the strengthening of west-high and east-low pressure system pattern in the future plays an important role in blocking TC from moving toward mid-latitudes of East Asia. The multiple linear regression model (MLRM) developed using six predictors (independent variables) analyzed from NCEP-NCAR reanalysis data predicts that total TC genesis frequency during July to October (JASO), which predicted using data of 20C3M, will have more (2?C3) TCs than in the present. 相似文献
256.
After the fuzzy clustering method (FCM) that analyzes the tracks of the tropical cyclones (TCs) struck the Korean peninsula (hereafter, K-TC) for a 60-year period (1951?C2010), it is found that both frequency and intensity of K-TC have been increased in recent years. In the order of the cluster number, both K-TC track pattern and its full-track pattern tended to shift southward. That is, while the passage frequency of TC in mainland China and the Manchurian regions decreased, it instead over the sea. Due to this decrease in the topographic effect on TC before reaching Korea, TC intensity around Korea became stronger. The vertical wind shear well reflected a TC intensity around Korea, which became weaker in mid-latitudes of East Asia. On the other hand, the peak month of K-TC frequency lags in the order of the cluster number. The two clusters that most TCs pass through the Korean Peninsula showed a stronger intensity and higher frequency before the 1970s. Meanwhile, another two clusters that most TCs pass through the Straits of Korea or the western region of the Japanese Islands showed those characteristics from the 1980s onward. Consequently, the changes in TC track, recurvature, frequency, and intensity around Korea were related to the southward shift of the western North Pacific high in the order of the cluster number. 相似文献
257.
We present suggestive evidence for an inverse energy cascade within Jupiter’s atmosphere through a calculation of the power spectrum of its kinetic energy and its cloud patterns. Using Cassini observations, we composed full-longitudinal mosaics of Jupiter’s atmosphere at several wavelengths. We also utilized image pairs derived from these observations to generate full-longitudinal maps of wind vectors and atmospheric kinetic energy within Jupiter’s troposphere. We computed power spectra of the image mosaics and kinetic energy maps using spherical harmonic analysis. Power spectra of Jupiter’s cloud patterns imaged at certain wavelengths resemble theoretical spectra of two-dimensional turbulence, with power-law slopes near −5/3 and −3 at low and high wavenumbers, respectively. The slopes of the kinetic energy power spectrum are also near −5/3 at low wavenumbers. At high wavenumbers, however, the spectral slopes are relatively flatter than the theoretical prediction of −3. In addition, the image mosaic and kinetic energy power spectra differ with respect to the location of the transition in slopes. The transition in slope is near planetary wavenumber 70 for the kinetic energy spectra, but is typically above 200 for the image mosaic spectra. Our results also show the importance of calculating spectral slopes from full 2D velocity maps rather than 1D zonal mean velocity profiles, since at large wavenumbers the spectra differ significantly, though at low wavenumbers, the 1D zonal and full 2D kinetic energy spectra are practically indistinguishable. Furthermore, the difference between the image and kinetic energy spectra suggests some caution in the interpretation of power spectrum results solely from image mosaics and its significance for the underlying dynamics. Finally, we also report prominent variations in kinetic energy within the equatorial jet stream that appear to be associated with the 5 μm hotspots. Other eddies are present within the flow collar of the Great Red Spot, suggesting caution when interpreting snapshots of the flow inside these features as representative of a time-averaged state. 相似文献
258.
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260.
Marie-Pierre Isaure Géraldine Sarret Yong-Eui Choi Sirine C. Fakra Sébastien Pairis Stephan Clemens Alain Manceau 《Geochimica et cosmochimica acta》2010,74(20):5817-5834
In tobacco plants, elimination of Zn and Cd via the production of Ca-containing grains at the top of leaf hairs, called trichomes, is a potent detoxification mechanism. This study examines how Cd is incorporated in these biominerals, and how calcium growth supplement modifies their nature. Scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX), microfocused X-ray diffraction (μ-XRD), and microfocused X-ray absorption near edge structure (μ-XANES) spectroscopy were used to image the morphology of the grains, identify the crystallized mineral phases, and speciate Cd, respectively. The mineralogy of the grains and chemical form of Cd varied with the amount of Ca. When tobacco plants were grown in a nutrient solution containing 25 μM Cd and low Ca supplement (Ca/Cd = 11 mol ratio), most of the grains were oblong-shaped and low-Cd-substituted calcite. When exposed to the same amount of Cd and high Ca supplement (Ca/Cd = 131 mol ratio), grains were more abundant and diverse in compositions, and in total more Cd was eliminated. Most grains in the high Ca/Cd experiment were round-shaped and composed predominantly of Cd-substituted vaterite, a usually metastable calcium carbonate polymorph, and subordinate calcite. Calcium oxalate and a Ca amorphous phase were detected occasionally in the two treatments, but were devoid of Cd. The biomineralization of cadmium and implications of results for Cd exposure of smokers and phytoremediation are discussed. 相似文献