岩溶洞穴次生碳酸盐沉积铀及其同位素组成古气候环境研究进展   总被引：1，自引：1，他引：0  

陈琼  陈琳  黄嘉仪  刘淑华  杨亮  米小建  周厚云 《中国岩溶》2015,34(5):479-485

洞穴沉积铀含量及其同位素初始234U/238U[（234U/238U)0]变化均与过去气候环境变化关系密切。文章分别对石笋中U含量和(234U/238U)0的气候意义进行统计分析发现,多数研究认为洞穴沉积U含量和(234U/238U)0可能指示土壤湿度和有效降水变化。然而,不管是对洞穴沉积的U含量还是(234U/238U)0,其气候环境意义解读还存在两种观点。但无论如何,这些研究成果都显示了洞穴沉积的U含量和(234U/238U)0是研究过去气候环境变化的重要替代指标。在未来的研究中,除了土壤环境和过程,还应关注U来源的相对贡献变化和其他微量元素与U元素的关系。这一指标可能在对东亚地区的大气粉尘活动和冬季风演化、地表生物量的变化研究等方面发挥重要作用。   相似文献   

被动桩水平位移荷载施加位置的探讨     

上官士青  杨敏  李卫超 《岩土力学》2015,36(10):2934-2938

被动桩是指一种由于土体水平位移而发生挠曲变形的桩。目前不论是室内试验还是数值计算,常在模型边界对土体施加水平位移荷载（位移边界条件）形成土体的位移场,用来研究被动桩的变形特征,但不同研究者采用的水平位移施加位置（边界位置）与被动桩的距离存在较大差异。结合一个工程案例,采用有限单元法对水平位移加载位置进行了单变量参数分析。研究表明,随着水平位移加载位置与被动桩距离的增加,桩身变形显著减小。这表明了施加位移边界后地基中存在明显的应力扩散。当该距离小于5.5倍桩径时,在模型边界施加同等大小的水平位移所需应力显著增加。同时讨论了水平荷载加载位置与被动桩距离的合理范围,认为应在5～8倍桩径范围之内。  相似文献   

纳微米聚合物微球的水化膨胀封堵性能   总被引：1，自引：0，他引：1  

李娟  朱维耀  龙运前  兰喜艳  杨智慧 《东北石油大学学报》2012,(3):52-57,8

为改善聚合物微球的深度调剖效果,利用蒸馏沉淀聚合法制备纳微米聚合物微球,并利用激光粒度分析仪、微孔滤膜装置和驱替装置对纳微米聚合物微球的粒径、水化膨胀能力和变形封堵能力进行测试分析.结果表明:纳微米聚合物微球为较规则均匀的球形,粒径分布集中,具有良好的水化膨胀性能;随着盐矿化度增大,纳微米聚合物微球膨胀性能变差;随着温度升高,微球的膨胀性能变强;在氯化钙和氯化镁水型中,微球膨胀性能变差;在酸性和碱性环境中,微球膨胀性能变差;随着水化时间增长,微球的封堵性能和变形能力逐渐增强,对孔道产生有效封堵的同时又能变形通过孔道,在渗透率较低的岩心中具有更好的深度调剖效果.  相似文献   

断裂密集带在油运聚成藏中的作用——以三肇凹陷和尚2井区块扶杨油层为例     

周广军 《东北石油大学学报》2012,(6):22-27,6

为研究三肇凹陷和尚2井区块扶杨油层油气成藏规律,采用断裂密集带与油气分布叠合的方法,分析断裂密集带在油气成藏分布中的作用.结果表明:三肇凹陷扶杨油层发育35条断裂密集带,尚2井区块扶杨油层发育9条断裂密集带;油主要分布在断裂密集带两侧,少量分布在断裂密集带内部.断裂密集带对油运移的控制作用表现在2方面:(1)断裂密集带边界断裂为油输导断裂;(2)断裂密集带不利于油横穿其侧向运移,但可沿其侧向运移.断裂密集带对油聚集的控制作用表现在2方面:(1)断裂密集带两侧的地垒和断阶构造是油聚集的有利部位;(2)断裂密集带内部的背形构造也是油聚集的有利部位.  相似文献   

线性Radon变换噪音压制法及其在古龙断陷中的应用   总被引：1，自引：1，他引：0  

石颖  李莹  王维红  陆加敏 《东北石油大学学报》2012,36(4):116-120,11

针对松辽盆地北部古龙断陷地震资料信噪比低、线性干扰强特点,提出应用线性Radon变换进行叠前线性噪音压制的预处理方法,Radon变换可在炮集和CMP道集上进行运算,算法简单,易于编程实现,其积分路径的特点适合线性噪音压制.模拟数据和实际地震资料应用结果表明,线性Radon变换法能够实现保幅的线性噪音压制,是叠前提高地震资料信噪比的实用方法,在地震资料预处理中具有应用前景.  相似文献   

无定形碳酸钙结合蛋白对鼠前成骨细胞MC3T3-E1碱性磷酸酶活性的影响     

万翔  孙娟  苏境坦  梁晓  张文权  郑桂兰  谢莉萍  王洪钟  张贵友  杜晓东  张荣庆 《广东海洋大学学报》2012,(3):13-18

以 MC3T3-E1细胞系为实验材料,探讨了真核表达的重组蛋白 rACCBP 对成骨细胞的作用.结果表明:rACCBP 对 MC3T3-E1的分化具有抑制作用,用含有0.001 g/mL rACCBP 的 DMEM 培养液,培养8 d 后细胞的ALP 活性仅为7.187 U/mg,远低于参照的11.917 U/mg; rACCBP 削弱了 dexamethane 和 ascorbic acid 对 MC3T3-E1的诱导作用  相似文献   

Numerical modelling of rise and fall of a dense layer in salt diapirs   总被引：4，自引：0，他引：4  

Z. Chemia  H. Koyi  H. Schmeling 《Geophysical Journal International》2008,172(2):798-816

Numerical models are used to study the entrainment of a dense anhydrite layer by a diapir. The anhydrite layer is initially horizontally embedded within a viscous salt layer. The diapir is down-built by aggradation of non-Newtonian sediments ( n = 4, constant temperature) placed on the top of the salt layer. Several parameters (sedimentation rate, salt viscosity, perturbation width and stratigraphic position of the anhydrite layer) are studied systematically to understand their role in governing the entrainment of the anhydrite layer. High sedimentation rates during the early stages of the diapir evolution bury the initial perturbation and, thus, no diapir forms. The anhydrite layer sinks within the buried salt layer. For the same sedimentation rate, increasing viscosity of the salt layer decreases the rise rate of the diapir and reduces the amount (volume) of the anhydrite layer transported into the diapir. Model results show that viscous salt is capable of carrying separate blocks of the anhydrite layer to relatively higher stratigraphic levels. Varying the width of the initial perturbation (in our calculations 400–800 m), from which a diapir triggers, shows that wider diapirs can more easily entrain an embedded anhydrite layer than the narrower diapirs. The anhydrite layer is entrained as long as rise rate of the diapir exceeds the descent rate of the denser anhydrite layer. We conclude that the four parameters mentioned above govern the ability of a salt diapir to entrain an embedded dense layer. However, the model results show that the entrained blocks inevitably sink back if the rise rate of the diapir is less than the rate of descent of the anhydrite layer or the diapir is permanently covered by a stiff overburden in case of high sedimentation rates.  相似文献   

Thin elastic shells with variable thickness for lithospheric flexure of one-plate planets     

Mikael Beuthe 《Geophysical Journal International》2008,172(2):817-841

Planetary topography can either be modelled as a load supported by the lithosphere, or as a dynamic effect due to lithospheric flexure caused by mantle convection. In both cases the response of the lithosphere to external forces can be calculated with the theory of thin elastic plates or shells. On one-plate planets the spherical geometry of the lithospheric shell plays an important role in the flexure mechanism. So far the equations governing the deformations and stresses of a spherical shell have only been derived under the assumption of a shell of constant thickness. However, local studies of gravity and topography data suggest large variations in the thickness of the lithosphere. In this paper, we obtain the scalar flexure equations governing the deformations of a thin spherical shell with variable thickness or variable Young's modulus. The resulting equations can be solved in succession, except for a system of two simultaneous equations, the solutions of which are the transverse deflection and an associated stress function. In order to include bottom loading generated by mantle convection, we extend the method of stress functions to include loads with a toroidal tangential component. We further show that toroidal tangential displacement always occurs if the shell thickness varies, even in the absence of toroidal loads. We finally prove that the degree-one harmonic components of the transverse deflection and of the toroidal tangential displacement are independent of the elastic properties of the shell and are associated with translational and rotational freedom. While being constrained by the static assumption, degree-one loads can deform the shell and generate stresses. The flexure equations for a shell of variable thickness are useful not only for the prediction of the gravity signal in local admittance studies, but also for the construction of stress maps in tectonic analysis.  相似文献   

Numerical inversion of deformation caused by pressure sources: application to Mount Etna (Italy)     

E. Trasatti  C. Giunchi  N. Piana Agostinetti 《Geophysical Journal International》2008,172(2):873-884

The interpretation of geodetic data in volcanic areas is usually based on analytical deformation models. Although numerical finite element (FE) modelling allows realistic features such as topography and crustal heterogeneities to be included, the technique is not computationally convenient for solving inverse problems using classical methods. In this paper, we develop a general tool to perform inversions of geodetic data by means of 3-D FE models. The forward model is a library of numerical displacement solutions, where each entry of the library is the surface displacement due to a single stress component applied to an element of the grid. The final solution is a weighted combination of the six stress components applied to a single element-source. The pre-computed forward models are implemented in a global search algorithm, followed by an appraisal of the sampled solutions. After providing extended testing, we apply the method to model the 1993–1997 inflation phase at Mt Etna, documented by GPS and EDM measurements. We consider four different forward libraries, computed in models characterized by homogeneous/heterogeneous medium and flat/topographic free surface. Our results suggest that the elastic heterogeneities of the medium can significantly alter the position of the inferred source, while the topography has minor effect.  相似文献   

Automatic classification of dome instabilities based on Doppler radar measurements at Merapi volcano, Indonesia: Part I     

M. Vöge  M. Hort 《Geophysical Journal International》2008,172(3):1188-1206

Monitoring lava dome instabilities is crucial to efficiently monitor active dome building volcanoes. The Doppler radar technique provides a unique opportunity to gather information about the number of instability events occurring at the growing dome and about the dynamic processes that take place during different types of instabilities. So far, three different kinds of processes have been identified: sliding material, gravitational break-offs and explosive outbursts. In addition, Doppler radars provide rain measurements, which can be used to investigate possible correlations between rainfall and dome activity. Two radar systems have been installed at Merapi volcano in October 2001 and January 2005 to continuously monitor dome instabilities. Due to the large number of instability events that occur during times of high activity, manual processing and analysis of instability events is not practical for monitoring purposes. Therefore, an automatic classification system has been developed, which is capable of identifying different kinds of instabilities as well as rainfall. Two different kinds of classifier models have been applied: (1) neural network and (2) K-nearest-neighbour classifier model. Both classify Doppler spectra according to the underlying dynamic process, that is, rain, sliding material, gravitational break-off or explosive outburst. The classifiers are able to identify disturbances, which have no physical source, but are merely artefacts from the radar device itself. Because radar events are sequences of Doppler spectra, a rule set has been defined, which finally determines the event class. All classifiers have been trained and tested on independent data sets to estimate the classification performance. The overall classification rate is about 90 per cent. Discrimination of instabilities and non-volcanic events reaches about 98 per cent accuracy.  相似文献