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991.
Boron resources are abundant in Da Qaidam salt lake of Qaidamu Basin. It has been given great attention for the polyborate species present in brine. In this study, the Raman spectroscopy was applied to investigate the existing-form of boron in brine during evaporation. The prepared solutions of MgO·2B2O3-H2O, MgO·2B2O3-MgCl2 -H2O, and MgO·2B2O3-MgSO4-H2O was also evaporated and recorded to study the influence of boron concentration, pH, and electrolytes on the borate speciation in brine. The mononborates of B(OH)3 and B(OH)4- were found to be the only forms present in the original salt lake brine. Brine evaporation promotes the formation of polyborate anions B3O3(OH)4-, B5O6(OH)4-, and B6O7(OH)62- and also disappearance of the B(OH)4- ion in brine with boron concentration of more than 11 g/L in B2O3. The pentaborate ion of B5O6(OH)4- was sensitive to the solution pH and found to be appeared under the pH value of 8.0. While the hexaborate ion of B6O7(OH)62- was observed more dependent on the electrolyte of magnesium chloride due to its special properties, such as promoting boron accumulation, lowering solution pH, and also the strong af?nity for water molecules, which is beneficial to the polymerization of borate ions in brine. The interaction mechanisms among polyborate anions during evaporation had also been proposed. 相似文献
992.
以添加不同掺量填料的氯氧镁水泥(MOC)试件为基体,在空气和碳化箱中分别养护至规定龄期,研究碳化对掺加填料MOC力学性能的影响,并与空气环境进行对比,运用XRD和SEM分析碳化后水化产物和微观结构的变化规律。结果表明,28 d龄期内,随着填料掺量的增加MOC试件碳化后的抗折强度均有所增加,碳化后的抗压强度均有提升,碳化过程反应生成了MgCO_3,不同碳化龄期的主要物相均为5Mg(OH)_2·MgCl_2·8H_2O(5相),而掺加填料不影响MOC的水化产物的组成。 相似文献
993.
Journal of Geographical Sciences - Rice (Oryza sativa L.) is the most important staple crop of China, and its production is related to both natural condition and human activities. It is fundamental... 相似文献
994.
本文采用中国沿海地区13个探空站2010~2014年实测地表温度Ts与平均温度Tm数据,利用傅里叶级数分析法精化中国沿海地区Tm模型,并将2015年探空站实测Tm数据与精化模型进行对比检验。结果表明,精化模型在Tm探测方面具有更高的计算精度,其计算大气可降水量的误差概率分布趋近于正态分布,具有较强的稳定性。 相似文献
995.
Chinese summer extreme rainfall often brings huge economic losses, so the prediction of summer extreme rainfall is necessary. This study focuses on the predictability of the leading mode of Chinese summer extreme rainfall from empirical orthogonal function(EOF) analysis. The predictors used in this study are Arctic sea ice concentration(ASIC) and regional sea surface temperature(SST) in selected optimal time periods. The most important role that Arctic sea ice(ASI) plays in the appearance of EOF1 may be strengthening the high pressure over North China, thereby preventing water vapor from going north. The contribution of SST is mainly at low latitudes and characterized by a significant cyclone anomaly over South China. The forecast models using predictor ASIC(PA), SST(PS), and the two together(PAS) are established by using data from 1980 to 2004. An independent forecast is made for the last 11 years(2005-2015). The correlation coefficient(COR) skills between the observed and cross-validation reforecast principal components(PC) of the PA, PS, and PAS models are 0.47, 0.66, and 0.76, respectively. These values indicate that SST is a major cause of Chinese summer extreme rainfall during 1980-2004. The COR skill of the PA model during the independent forecast period of 2004-2015 is 0.7, which is significantly higher than those of the PS and PAS models. Thus, the main factor influencing Chinese summer extreme rainfall in recent years has changed from low latitudes to high latitudes. The impact of ASI on Chinese summer extreme rainfall is becoming increasingly significant. 相似文献
996.
HU Huiqin HUANG Fei ZHANG Shaoqing RUAN Chengqing GAO Shanhong LI Pengyuan 《中国海洋大学学报(英文版)》2019,(2):271-281
Fog has recently become a frequent high-impact weather phenomenon along the coastal regions of North China. Accurate fog forecasting remains challenging due to limited understanding of the predictability and mechanism of fog formation associated with synoptic-scale circulation. One frequent synoptic pattern of fog formation in this area is associated with cold front passage(cold-front synoptic pattern, CFSP). This paper explored the predictability of a typical CFSP fog event from the perspective of analyzing key characteristics of synoptic-scale circulation determining fog forecasting performance and the possible mechanism. The event was ensemble forecasted with the Weather Research and Forecasting model. Two groups of ensemble members with good and bad forecasting performance were selected and composited. Results showed that the predictability of this case was largely determined by the simulated strengths of the cold-front circulation(i.e., trough and ridge and the associated surface high). The bad-performing members tended to have a weaker ridge behind a stronger trough, and associated higher pressure over land and a weaker surface high over the sea, leading to an adverse impact on strength and direction of steering flows that inhibit warm moist advection and enhance cold dry advection transported to the focus region. Associated with this cold dry advection, adverse synoptic conditions of stratification and moisture for fog formation were produced, consequently causing failure of fog forecasting in the focus region. This study highlights the importance of accurate synoptic-scale information for improved CFSP fog forecasting, and enhances understanding of fog predictability from perspective of synoptic-scale circulation. 相似文献
997.
In this study, we used Landsat images and meteorological data to examine the spatiotemporal distribution and variability of sea ice in Jiaozhou Bay(JZB) between 1986 and 2016. The results show that JZB is not always covered by sea ice in winter, but in some extreme cases, sea ice has covered more than one-third of the sea area of the bay. Sea ice in JZB has generally formed between January 1 and February 5, primarily along the coast, and gradually expanding to the central area of the bay. Both meteorological and artificial factors have played important roles in modulating the sea ice distribution. We found sea ice coverage to have been strongly correlated with the accumulated freezing-degree days nine days before the occurrence of sea ice(R2 = 0.767). North-northwest surface winds have dominated the freezing period of sea water in the JZB, and wind speed has exerted a more significant influence on the formation of sea ice when the sea ice coverage has been generally small. Additionally, artificial factors began to affect the expansion of sea ice in JZB since 2007. The construction of the Jiao-Zhou-Bay Bridge(JZBB) is believed to have retarded water flow and reduced the tidal prism, thereby leading to the formation of an ice bridge along the JZBB, which effectively prevents the southward expansion of sea ice. 相似文献
998.
Recently, various toppling slopes have emerged with the development of hydropower projects in the western mountainous regions of China. The slope on the right bank of the Laxiwa Hydropower Station, located on the mainstream of the Yellow River in the Qinghai Province of Northwest China, is a typical hard rock slope. Further, its deformation characteristics are different from those of common natural hard rock toppling. Because this slope is located close to the dam of the hydropower station, its deformation mechanism has a practical significance. Based on detailed geological engineering surveys, four stages of deformation have been identified using discrete element numerical software and geological engineering analysis methods, including toppling creep, initial toppling deformation, intensified toppling deformation, and current slope formation. The spatial and time-related deformation of this site also exhibited four stages, including initial toppling, toppling development, intensification of toppling, and disintegration and collapse. Subsequently, the mechanism of toppling and deformation of the bank slope were studied. The results of this study exhibit important reference value for developing the prevention–control design of toppling and for ensuring operational safety in the hydropower reservoir area. 相似文献
999.
Silty sand can be prone to erosion because it is short of stability cementation materials. In recent years, various emerging soil stabilizers, especially natural organic substance and polymer, have been used to improve soil strength, water stability and ability of erosion resistance. In this study, a new type of soil stabilization additive modified carboxymethyl cellulose(M-CMC), consisting of carboxymethyl cellulose(CMC) and polyacrylamide(PAM), was developed for stabilization treatment of silty sand. A series of laboratory tests were conducted to evaluate the performance of M-CMC application on shear strength, permeability, water susceptibility and microstructure of the silty sand soil treated with additive concentration range of 0%-1.3%. Moreover, rainfall simulation experiments were conducted to evaluate the effect of M-CMC on the erosion control of silty sand which compacted soil in a large-sized runoff(1 m~2) plots. Test plot which treated with 1.1% concentration of soil stabilizer and control plot which treated with same amount of water were cured outdoor for 50 days before rainfall simulation test. Rainfall intensity was applied at 120 mm·h-1 for 60 min. Finally, a field test is performed in order to assess the practical application effect of silty sand with 1.1% M-CMC. In general, the results showed that an increase of the concentration of M-CMC resulted in an improvement in water susceptibility and shear strength but a decrease in the infiltration rate. Internal friction angle of the treated soil remarkably increased under a low M-CMC concentration(less than 0.7%), while cohesion of them sharply increased under a relatively high M-CMC concentration(larger than 0.7%). Water susceptibility of the treated samples was improved remarkably under a relatively high M-CMC concentration(larger than 0.7%). Permeability coefficient of them decreased significantly when the M-CMC concentration was increased from 0 to 0.5% and, then, from 0.9% to 1.3%. Based on the images obtained from a scanning electron microscopy(SEM), the "coating" and "netting" effects were attributable to the observed improvement of the treated soil. When a plot was protected by a thin layer of soil treated with 1.1% MCMC, its erosion resistance was greatly improved, infiltration rate of water and soil loss yield of plot decreased greatly and even though under a rainfall intensity of 120 mm·h-1. The field test with long-term monitoring(three years) confirmed the M-CMC can effectively control erosion of silty sand slopes for a prolonged period of time. 相似文献
1000.