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901.
902.
Wang Kai-Rang Lin Jun Liu Lian-Guang Liu Chun-Ming Gao Guan-Nan 《Chinese Astronomy and Astrophysics》2012
Solar activities can cause the anomalies of electric power transmission systems, especially, for an extra-long distance transmission system. Using the data of coronal mass ejection (CME) from SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph), and the data of the geomagnetically induced current (GIC) and geomagnetic storm from the North China Electric Power University and Finnish Meteorological Institute, respectively, we analyze some important observational features and physical properties of the earth-directed halo CMEs associated with the GIC events. After classifying the observed halo CMEs according to their symmetry, it is found that the halo CMEs associated with GIC events are mainly the 3 types: completely symmetric, brightness-asymmetric, and outline-asymmetric. The geomagnetically induced current events driven by the three different types of halo CMEs have different characteristics in the intensity, duration, and period. We ?nd that the brightness-asymmetric halo CMEs are most likely to cause the major damage to the transmission systems. And that the geomagnetically induced current has also a good correlation with the time variation of geomagnetic ?eld. 相似文献
903.
904.
905.
Yan Guo Herong Gui Jiuchuan Wei Zhi Zhang Mancong Hu Pei Fang Guangping Li Chuan Gao Xin Wang 《Ground water》2021,59(2):256-265
Permian coal measure sandstone fissure water (referred to as “coal measure water,” that is, water in coal measures) is one of the important water sources for industrial and agricultural activities in mining areas. However, the regional high-pressure grouting, one of the most widely used floor control methods, may affect the coal measure water which is connected with limestone aquifer. This study used Taoyuan mine, a typical coal mine in Huaibei coalfield, as the research area to study the influencing mechanism of a grouting treatment on the hydrogeochemical evolution of coal measure water. The hydrogeochemical characteristics and water-rock interaction mechanism of the coal measure water before and during the treatment were evaluated using a Piper trigram, ion combination ratio, and hydrogen-oxygen stable isotope. The anions and cations in the coal measure water before and during the treatment had the same trends at SO42− > HCO3− > Cl− and Na+ > Ca2+ > Mg2+, respectively. Hydrochemical types of coal measure water before treatment were mainly SO4·Cl-Ca·Mg, SO4·Cl-Na, and HCO3-Na, and during treatment they were mainly SO4·Cl-Na and HCO3-Na. The formation of chemical components of coal measure water before treatment was mainly caused by carbonate dissolution, sulfate dissolution, and pyrite oxidation. During the treatment, sulfate dissolution and pyrite oxidation were the main geochemical processes, and ion exchange was enhanced. Atmospheric precipitation was the source of all water samples, and all showed an obvious 18O drift. 相似文献
906.
The simplified macro‐equations of porous elastic media are presented based on Hickey's theory upon ignoring effects of thermomechanical coupling and fluctuations of porosity and density induced by passing waves. The macro‐equations with definite physical parameters predict two types of compressional waves (P wave) and two types of shear waves (S wave). The first types of P and S waves, similar to the fast P wave and S wave in Biot's theory, propagate with fast velocity and have relatively weak dispersion and attenuation, while the second types of waves behave as diffusive modes due to their distinct dispersion and strong attenuation. The second S wave resulting from the bulk and shear viscous loss within pore fluid is slower than the second P wave but with strong attenuation at lower frequencies. Based on the simplified porous elastic equations, the effects of petrophysical parameters (permeability, porosity, coupling density and fluid viscosity) on the velocity dispersion and attenuation of P and S waves are studied in brine‐saturated sandstone compared with the results of Biot's theory. The results show that the dispersion and attenuation of P waves in simplified theory are stronger than those of Biot's theory and appear at slightly lower frequencies because of the existence of bulk and shear viscous loss within pore fluid. The properties of the first S wave are almost consistent with the S wave in Biot's theory, while the second S wave not included in Biot's theory even dies off around its source due to its extremely strong attenuation. The permeability and porosity have an obvious impact on the velocity dispersion and attenuation of both P and S waves. Higher permeabilities make the peaks of attenuation shift towards lower frequencies. Higher porosities correspond to higher dispersion and attenuation. Moreover, the inertial coupling between fluid and solid induces weak velocity dispersion and attenuation of both P and S waves at higher frequencies, whereas the fluid viscosity dominates the dispersion and attenuation in a macroscopic porous medium. Besides, the heavy oil sand is used to investigate the influence of high viscous fluid on the dispersion and attenuation of both P and S waves. The dispersion and attenuation in heavy oil sand are stronger than those in brine‐saturated sandstone due to the considerable shear viscosity of heavy oil. Seismic properties are strongly influenced by the fluid viscosity; thus, viscosity should be included in fluid properties to explain solid–fluid combination behaviour properly. 相似文献
907.
The Qinghai–Tibet Plateau has a vast area of approximately 70×104 km2 of alpine meadow under the impacts of soil freezing and thawing, thereby inducing intensive water erosion. Quantifying the rainfall erosion process of partially thawed soil provides the basis for model simulation of soil erosion on cold-region hillslopes. In this study, we conducted a laboratory experiment on rainfall-induced erosion of partially thawed soil slope under four slope gradients (5, 10, 15, and 20°), three rainfall intensities (30, 60, and 90 mm h−1), and three thawed soil depths (1, 2, and 10 cm). The results indicated that shallow thawed soil depth aggravated soil erosion of partially thawed soil slopes under low hydrodynamic conditions (rainfall intensity of 30 mm h−1 and slope gradient ≤ 15°), whereas it inhibited erosion under high hydrodynamic conditions (rainfall intensity ≥ 60 mm h−1 or slope gradient > 15°). Soil erosion was controlled by the thawed soil depth and runoff hydrodynamic conditions. When the sediment supply was sufficient, the shallow thawed soil depth had a higher erosion potential and a larger sediment concentration. On the contrary, when the sediment supply was insufficient, the shallow thawed soil depth resulted in lower sediment erosion and a smaller sediment concentration. The hydrodynamic runoff conditions determined whether the sediment supply was sufficient. We propose a model to predict sediment delivery under different slope gradients, rainfall intensities, and thawed soil depths. The model, with a Nash–Sutcliffe efficiency of 0.95, accurately predicted the sediment delivery under different conditions, which was helpful for quantification of the complex feedback of sediment delivery to the factors influencing rainfall erosion of partially thawed soil. This study provides valuable insights into the rainfall erosion mechanism of partially thawed soil slopes in the Qinghai–Tibet Plateau and provides a basis for further studies on soil erosion under different hydrodynamic conditions. 相似文献
908.
Jianhui Wei Ningpeng Dong Benjamin Fersch Joël Arnault Sven Wagner Patrick Laux Zhenyu Zhang Qianya Yang Chuanguo Yang Shasha Shang Lu Gao Zhongbo Yu Harald Kunstmann 《水文研究》2021,35(8):e14341
The regional terrestrial water cycle is strongly altered by human activities. Among them, reservoir regulation is a way to spatially and temporally allocate water resources in a basin for multi-purposes. However, it is still not sufficiently understood how reservoir regulation modifies the regional terrestrial- and subsequently, the atmospheric water cycle. To address this question, the representation of reservoir regulation into the terrestrial component of fully coupled regional Earth system models is required. In this study, an existing process-based reservoir network module is implemented into NOAH-HMS, that is, the terrestrial component of an atmospheric–hydrologic modelling system, namely, the WRF-HMS. It allows to quantitatively differentiate role of reservoir regulation and of groundwater feedback in a simulated ground-soil-vegetation continuum. Our study focuses on the Poyang Lake basin, where the largest freshwater lake of China and reservoirs of different sizes are located. As compared to streamflow observations, the newly extended NOAH-HMS slightly improves the streamflow and streamflow duration curves simulation for the Poyang Lake basin for the period 1979–1986. The inclusion of reservoir regulation leads to major changes in the simulated groundwater recharges and evaporation from reservoirs at local scale, but has minor effects on the simulated soil moisture and surface runoff at basin scale. The performed groundwater feedback sensitivity analysis shows that the strength of the groundwater feedback is not altered by the consideration of reservoir regulation. Furthermore, both reservoir regulation and groundwater feedback modify the partitioning of the simulated evapotranspiration, thus affecting the atmospheric water cycle in the Poyang Lake region. This finding motivates future research with our extended fully coupled atmospheric–hydrologic modelling system by the community. 相似文献
909.
910.