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961.
《Chemie der Erde / Geochemistry》2017,77(1):183-194
The Naga Ophiolite Belt is a part of the Naga-Arakan-Yoma flysch trough that occurs along the Indo-Myanmar border. It is represented by peridotites, mafic-ultramafic cumulates, mafic volcanics, mafic dykes, plagiogranites, pelagic sediments and minor felsic to intermediate intrusives. Minor plagiogranites, gabbros and thin serpentinite bands occur juxtaposed near Luthur, with the slate-phyllite-metagreywacke sequence (Phokpur Formation) adjacent to the contact. The development of tonalites, trondhjemites and diorites in the oceanic crust, which is grouped as plagiogranites, offers an opportunity to study the process of formation of silicic melts from mafic crust. Plagiogranites from Naga Ophiolite Belt contains moderate SiO2 (51.81–56.71 wt.%), low K2O (0.08–1.65 wt.%) and high Na2O (4.3–5.03 wt.%). The Naga Ophiolite Belt plagiogranites like ocean-ridge granites contain low K2O, high Na2O and CaO. The rocks investigated from Naga Ophiolite Belt contain TiO2 concentrations above the lower limit for fractionated Mid Oceanic Ridge Basalt which is above 1 wt% of TiO2 and the ternary plots of A (Na2O + K2O) F(FeOT) M(MgO) and TiO2-K2O-SiO2/50 indicate that the plagiogranite are tholeiitic in character and gabbro samples are calc-alkaline in nature. The plagiogranites are enriched in Rb, Ba, Th, U, Nb and Sm against chondrite with negative anomalies on Sr and Zr whereas Y and Yb are depleted to Mid Oceanic Ridge Basalt. The chondrite normalized REE patterns of the plagiogranite display enrichments in LREE (LaN/SmN: 2.37–3.62) and flat HREE (Eu/Eu*: 0.90–1.06). The Mid Oceanic Ridge Basalt normalization of gabbro is characterized by strong enrichment of LILE like Ba and Th. The REE pattern is about 50–100 times chondrite with slight enrichment of LREE (LaN/SmN = 2.21–3.13) and flat HREE (Eu/Eu*: 0.94–1.19). The major-element and trace element data of the NOB plagiogranites and their intrusive nature with host gabbroic rock suggest that the plagiogranites were produced by fractional crystallization of basaltic parental magmas at Mid Oceanic Ridge. 相似文献
962.
钻井液流变性是钻井液流动和变形的特性,对于携带与悬浮岩屑、提高钻进速度至关重要,准确掌握钻井液流变参数是保证井眼清洁与高效钻进的前提。提出一种基于卷积神经网络(Convolutional Neural Network,CNN)的钻井液流变参数智能识别方法,通过磁力搅拌产生稳定的钻井液流动图像,利用多种数据增强方法增加图像数量并建立数据库,增强模型的鲁棒性和泛化能力。优化AlexNet卷积神经网络算法,构建钻井液流变参数识别模型。将数据库划分为训练集:验证集:测试集=7:2:1,对训练集进行迭代训练并通过验证集调整参数获得最佳拟合模型。此外,运用混淆矩阵、卷积核可视化技术和类激活技术(Gradient-weighted Class Activation Mapping,Grad-CAM)对模型进行多方位评估。结果表明:(1)钻井液流变参数识别模型对钻井液塑性黏度测试的宏精确率为95.2%,宏召回率为94.7%,宏
963.
Trust-region based instantaneous optimal semi-active control of long-span spatially extended structures with MRF-04K damper 总被引:1,自引:0,他引:1
In the field of civil engineering, magnetorheological fluid (MRF) damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm (TIOC) is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases. 相似文献
964.
965.
966.
利用高精度的MTS材料实验系统,在1473-1673K的温度区间和可控热力学环境条件下,对[100]pc和[110]pc两个方位的CaTiO3-钙钛矿单晶体进行了高温蠕变试验,着重观测了晶体结构相变和高温流变的相关性.研究表明,钙钛矿的晶体结构相变对其高温流变性质有明显影响,斜方晶系钙钛矿蠕变强度大大高于四方和立方晶系钙钛矿,后两者具有很强的高温塑性各向异性.在分析相变过程晶体结构变化特征和观测到的高温流变数据基础上,认为钙钛矿晶体结构相变中发生的位错结构的变化是导致其高温流变性变化的主要物理机制. 相似文献
967.
西藏扎布耶湖ZK91-2钻孔沉积特征与气候环境演化 总被引:12,自引:1,他引:12
扎布耶盐湖位于西藏高原腹地,1991年在其南部干盐滩中钻取了20m深湖相沉积,以5~10cm/个的密度进行高分辨率取样,详细探讨了沉积标志、矿物组合(尤其Mg、Ca、Li碳酸盐)、干旱与潮湿两种气候类型的元素组合等气候环境指标,推导了晚更新世以来该湖区湖面涨缩、水质咸谈及气温高低变化。 相似文献
968.
969.
970.
Present-day tectonic movement in the northeastern margin of the Qinghai-Xizang (Tibetan) plateau as revealed by earthquake activity 总被引:2,自引:0,他引:2
Characteristics of present-day tectonic movement in the northeastern margin of Qinghai-Xizang plateau (Tibetan) are studied
based on earthquake data. Evidence of earthquake activity shows that junctures between blocks in this area consist of complicated
deformation zones. Between the Gansu-Qinghai block and Alxa block there is a broad compressive deformation zone, which turns
essentially to be a network-like deformation region to the southeast. The Liupanshan region, where the Gansu-Qinghai block
contacts the Ordos block, is suffering from NE-SW compressive deformation. Junction zone between the Ordos and Alxa block
is a shear zone with sections of variable trend. The northwestern and southeastern marginal region of the Ordos is under NNW-SSE
extension. The above characteristics of present-day tectonic deformation of the northeastern Qinghai-Xizang plateau may be
attributed to the northeastward squeezing of the plateau and the resistance of the Ordos block, as well as the southeastward
extrusion of the plateau materials.
Foundation item: State Natural Science Foundation of China (49732090) and the Development Program on National Key Basic Researches under
the Project Mechanism and Prediction of Continental Strong Earthquakes (95-13-02-05).
Contribution No. 00FE2003, Institute of Geophysics, China Seismological Bureau. 相似文献