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131.
搜集2008年1月-2010年5月东北地区ML≥4.0地震波形资料,利用邻省多台P波初动资料,采用P波初动解计算方法,求解2008年1月-2010年5月东北地区ML≥4.0地震的震源机制解.结合前期工作成果,研究东北地区应力场方向的总体特征和主压、主张应力轴方向的变化,分析P轴走向随时间的变化与东北地区中强地震发生可能... 相似文献
132.
Suxiang Wu Honglei Fan Qian Zhang Yan Cheng Qian Wang Guanying Yang Buxing Han 《洁净——土壤、空气、水》2011,39(6):572-576
The conversion of the biomass into high value‐added chemicals is an attractive topic in green chemistry. In this work, we studied the synthesis of 2,6‐deoxyfructosazine (2,6‐DOF) and 2,5‐deoxyfructosazine (2,5‐DOF) from cellobiose and inulin, respectively, in aqueous solution by an one‐pot two‐step route. In this method, cellobiose or inulin was first hydrolyzed into glucose or fructose and then reacted directly with ammonium formate to form 2,6‐DOF or 2,5‐DOF. The effects of reaction temperature, reaction time, pH value on the yields of the products were studied. It was demonstrated that the cellobiose and inulin could be converted to 2,6‐DOF and 2,5‐DOF effectively at optimized condition. 相似文献
133.
Water outbursts from the floor during underground mining, and those from the surrounding rock mass of tunnels, involve the basic principle of hydraulic fracturing. Based on the hydraulic-fracturing mechanism, considered to be dependent on the coupling between seepage and damage, it is deemed that the variation of the pore-fluid pressure coefficient must be taken into account during this coupled process, in order to correctly establish the crack propagation mechanism during hydraulic fracturing. The coupled seepage-damage model is validated using numerical simulations of hydraulic fracturing around one hole and three holes; the model may also enable scientific and reasonable explanation of the dominance of hydraulic gradient on the crack propagation path in permeable rock. Finally, the water outburst from the floor at a coal mining site in Hebei Province, China, is numerically simulated, and the coupled seepage and damage mechanism during the mining-induced rock failure is clarified. The numerical simulation implies that the seepage-damage is the main mechanism for controlling the water outburst. Therefore this mechanism should be considered in the numerical simulation to understand the essence of water outburst induced in mines. 相似文献
134.
Laurence A. Lewis Gert Verstraeten Honglei Zhu 《International journal of geographical information science》2013,27(7):809-829
The RUSLE (Revised Universal Soil Loss Equation) is integrated within a GIS framework to calculate soil loss spatially. For this module, algorithms and procedures were developed to derive the slope length factor (L) and steepness factor (S) from a DEM, then integrated with the R, K, C, and P factors to develop homogeneous patches (sub‐units) within each field or river basin. Soil loss is determined for each patch within a study unit, and then combined to determine the fields' or river basin's average annual and total soil loss. Two case studies are presented. The first case study, in central Massachusetts, compares estimated soil loss values obtained for individual fields using the Idrisi RUSLE module to USDA‐NRCS RUSLE field data. While soil loss results were similar, the RUSLE module allows fields to be partitioned into more similar units than practical in the field. This permits detailed spatial analysis of soil‐loss patterns. The second case study compares soil‐loss estimates for a catchment in southwestern Flanders, Belgium. This model–model comparison contrasts the results from the RUSLE module to the WATEM model—a grid cell based model based on the USLE/RUSLE but conceptualized in a multi‐flow context. Results between the predicted soil losses utilizing the two different approaches are significantly correlated. However, estimated soil losses are consistently higher for the WATEM model. This likely reflects the differences between how the two models compute L as well as the contribution of ephemeral gullies and flow convergence which are incorporated in WATEM but not in RUSLE. 相似文献
135.
本文利用气体组分及大气气溶胶在线监测系统(MARGA ADI 2080)观测武汉市2018年1月9—26日大气气溶胶中的8种水溶性离子(NH+4、NO-3、SO2-4、Cl-、K+、Ca2+、Na+和Mg2+),结合气象要素数据,使用主成分分析(PCA)、正定矩阵因子分析法(PMF)、HYSPLIT后向轨迹模式、潜在源区贡献(PSCF)和浓度权重轨迹(CWT),对霾污染过程中水溶性离子进行了全面的来源解析,探究了霾不同阶段下来源差异和空间分布特征。结果表明:(1)本次霾污染中的8种水溶性离子和4种污染气体,PCA解析出的源和占比分别为二次源和燃煤源的混合源(41.28%)、工业排放和土壤扬尘混合源(27.73%)和机动车排放源(9.63%),PMF解析出的源和占比分别为燃煤与土壤扬尘混合源(18.57%)、机动车排放源(20.74%)、二次源(18.30%)、光化学污染源(22.24%)和燃煤源(20.15%)。(2)霾在不同阶段下水溶性离子和4种污染气体的来源存在差异,在清洁天和霾消散阶段,光化学的贡献最高,占比分别为31.42%和36.07%;在霾发生阶段燃煤与土壤扬尘源的贡献最高,其贡献为40.94%;在霾发展阶段,最大的控制源为二次源,贡献占比为37.51%。(3)此次武汉市霾污染中PM2.5浓度和NH+4、NO-3和SO2-4的潜在源区为皖豫鄂三省和赣湘鄂三省交界处。霾污染中PM2.5的主要影响范围是武汉市南部和北部省份,NO-3、NH+4和SO2-4的主要影响区域为武汉市东北方向的城市、湖南省和江西省。 相似文献
136.
137.
Permafrost changes under natural sites along the Qinghai-Tibet Railway were investigated based on the ground temperature monitored from the year of 2006 to 2015. Among these sites, mean permafrost table was 3.54 m, with a range of 0.88 to 9.14 m. Among the sites with decreasing permafrost table, mean decreasing amplitude of permafrost table was 0.51 m, with a range of 0.05 to 2.22 m; mean decreasing rate of permafrost table was 0.07 m/a, with a range of 0.01 to 0.25 m/a. Decreasing amplitude and decreasing rate of permafrost table in high temperature regions were 0.47 m and 0.06 m/a greater than those in low temperature regions, respectively. In general, ground temperatures at permafrost table and 15 m depth presented rising tendency. Mean rising amplitude of ground temperature at permafrost table was 0.16 ℃, with a range of 0.01 to 0.60 ℃; mean rising rate of ground temperature at permafrost table was 0.018 ℃/a, with a range of 0.001 to 0.067 ℃/a. Rising amplitude and rising rate of ground temperature at permafrost table in low temperature regions were 0.12 ℃ and 0.014 ℃/a greater than those in high temperature regions, respectively. Mean rising amplitude of ground temperature at 15 m depth was 0.10 ℃, with a range of 0.01 to 0.48 ℃; mean rising rate of ground temperature at 15 m depth was 0.011 ℃/a, with a range of 0.002 to 0.054 ℃/a. Rising amplitude and rising rate of ground temperature at 15 m depth in low temperature regions were 0.11 ℃ and 0.012 ℃/a greater than those in high temperature regions, respectively. Due to the effect of local factors, increasing of permafrost table and decreasing of ground temperature were observed under several sites. 相似文献
138.
139.
水泥改良冻土在融化压缩下的微观孔隙演变特征研究,对了解水泥改良冻土的过程具有重要意义。将水泥改良后的冻土进行融化压缩实验,通过冷冻干燥法对试验后的土样进行电镜样品制取并获取其微观特征图像。对试验土样进行比重测试,得到土样真实的三维孔隙比。最后以真实孔隙比作参考,确定图像分割所选取的灰度值并提取其孔隙特征。结合融化压缩试验结果,对水泥改良冻土的孔隙数量、面积、定向角及丰度值随改良土压缩量的变化关系进行了分析。研究结果表明:经过水泥改良后的冻土,大孔隙结构强度增大明显;随着水泥掺量及养护龄期的增加,孔隙比与孔隙面积变大,压缩量变小;随着土体压缩量的增大,孔隙的定向角分布逐渐由均匀状向锯齿状发展;土样压缩过程中,丰度值大于0.5的孔隙发生压缩明显,孔隙逐渐趋于细长状,并且随着压缩量的增大,孔隙丰度值的分布越来越趋于正态分布。孔隙微观结构演变研究为阐释水泥改良冻土宏观力学特性增强的机制提供了科学依据。 相似文献
140.