新疆阿斯塔那古墓群出土彩塑马尾装饰物的科学分析     

陈涛  贺婧婧  姚书文  邱振威  麦慧娟  王博  蒋洪恩 《第四纪研究》2019,39(1):258-263

阿斯塔那古墓群是新疆发现的最为重要的历史时期遗址之一,一直以来备受学术界关注。由于吐鲁番盆地气候炎热干燥,阿斯塔那古墓群保存下了数以万计的珍贵文物,其中包括颇为少见的各种泥俑。文章利用红外光谱、纤维旋转实验和显微形态观察等方法对阿斯塔那古墓群出土彩塑泥俑的马尾装饰物进行了科学分析,结果显示这些纤维来自于原产于近东、地中海沿岸的亚麻(Linum usitatissimum L.)。同时,结合出土文书,探讨了唐代吐鲁番地区亚麻的栽培利用状况,为深入认识亚麻传入中国的时间和路线提供了新的科学依据。  相似文献   

碳酸盐烃源岩排烃的若干特点   总被引：1，自引：3，他引：1  

汪本善  张丽洁 《地球化学》1996,25(4):317-323

通过典型碳酸盐型油气田的野外调查研究和对未成熟碳酸盐生油岩在外加温、外加压条件下所作的生烃一排烃模拟实验结果，获得下列新的认识：（１）碳酸盐烃源岩排烃的驱动力主要不是来自地层的压实作用，而是由于生烃过程中分子体积膨胀所产生的内应力（即生烃增压）。该应力与周围环境形成潜在的压力梯度，这是排驱动力的内在因素。但是单凭此因素尚不足以造成排烃，只有当后来烃源层受到外力作用（如导致微裂隙产生的区域性构造活动、造成溶蚀交代出现缝缝洞洞的地下水活动等）生成裂隙空间，并在源岩与裂隙间出现真正的压差时，才引发烃源层中积蓄的应力释放，从而造成排烃。因此、区域性的外力作用是排烃的控制因素。（２）碳酸盐烃源岩中生烃时间甚早，一般在Ｒ＿０为０．４５％左右时就开始生成低熟原油。但由于碳酸岩岩石粒间孔径甚小，虽有低熟油生成，却不能象泥质烃源岩那样在其烃浓度超过最低石油运移饱和度时就可排烃。事实证明，无论生烃量多大，只要碳酸盐烃源岩中不出现有效的通道，排烃作用可能永远不会进行。因此，当碳酸盐烃源岩中油气生成之后，裂隙发生的时间就成为决定碳酸盐烃源岩排烃时间的基本因素。（３）碳酸盐烃源岩中烃类初次运移基本上是以全烃相进行的，这与碳酸盐岩在后  相似文献   

用Pb-Pb同位素方法直接测定石炭系碳酸盐岩珊瑚化石年龄   总被引：5，自引：1，他引：5  

高劢  刘敦一  李永安 《地质论评》1996,42(1):22-29,T001

在地球化学领域中,直接解决沉积层序和早期成岩时代的定年问题长期以来被证明是具有挑战性的问题之一。用Pb-Pb同位素方法直接测定沉积碳酸盐岩的年龄是最近几年才发展起来的。本文报道了一个成功的研究新疆珊瑚年龄的例子,得到了石炭系珊瑚化石的年龄为344±7Ma,它与古生物学确定的年龄十分吻合。得到另一组年龄为334±25Ma,它的地质意义在进一步讨论中。这一结果表明,我们可以从单一珊瑚样品中得到一个精确的地层年龄,碳酸盐测年技术在建立沉积层序的绝对年代学中具有相当大的潜力。  相似文献   

Geometric and aerodynamic roughness of sea ice   总被引：2，自引：0，他引：2  

S. Mai  C. Wamser  C. Kottmeier 《Boundary-Layer Meteorology》1996,77(3-4):233-248

The aerodynamic drag of Arctic sea ice is calculated using surface data, measured by an airborne laser altimeter and a digital camera in the marginal ice zone of Fram Strait. The influence of the surface morphology on the momentum transfer under neutral thermal stratification in the atmospheric boundary layer is derived with the aid of model concepts, based on the partitioning of the surface drag into a form drag and a skin drag. The drag partitioning concept pays attention to the probability density functions of the geometric surface parameters. We found for the marginal ice zone that the form drag, caused by floe edges, can amount to 140% of the skin drag, while the effect of pressure ridges never exceeded 40%. Due to the narrow spacing of obstacles, the skin drag is significantly reduced by shadowing effects on the leeward side of floe edges. For practical purposes, the fractional sea-ice coverage can be used to parameterize the drag coefficientC _dn, related to the 10 m-wind. C _dnincreases from 1.2 · 10^-3 over open water to 2.8 · 10^-3 for 55% ice coverage and decreases to 1.5 · 10^-3 for 100% ice coverage.Aircraft turbulence measurements are used to compare the model values of C _dnwith measureents. The correlation between measured and modelled drag coefficients results in r ² = 0.91, where r is the correlation coefficient.  相似文献   

江西柘林水电站扩建工程安全监测分析     

何迈  肖本职  景峰 《岩土力学》2003,(Z1)

对江西柘林水电站扩建工程80山包施工监测布置及成果进行了介绍,并对监测成果进行了分析,安全监测在工程施工中发挥了重要作用。  相似文献   

两种基桩无损检测方法的比较     

潘纪顺  梁慧云  姬计法  张麦  刘志伟  吕芝全  王碧辉 《地震研究》2001,24(4):370-374

通过一个工程实例，对比了应力波反射法和地质雷达仪检测基桩的效果，阐明了地质雷达检测基桩桩身质量的独特优势。  相似文献   

碳酸盐岩振动液化地震序列   总被引：180，自引：16，他引：180  

乔秀夫  宋天锐 《地质学报》1994,68(1):16-34,T002

新建立的振动液化地震序列系碳酸盐软沉积物中的强地震事件记录，包括地震液化阶段产生的泄水脉、液化变形；液化停止后的地面下沉构造；地震引起的津浪丘状层与浊积岩等序列单元。这个序列来自大区域的野外实践总结，反映了一次强地震事件的全过程，并在理论上得到统一的解释。序列将为野外地质学家在碳酸盐层中识别事件提供对比的标准。根据振动液化地震记录，本文首次提出古郯庐带概念，并对其地质意义进行了初步讨论。  相似文献   

An off-and-towards-equilibrium strategy for vibrational control of structures     

杨润林  童迈  周锡元  闫维明  刘锡荟 《地震工程与工程振动(英文版)》2006,5(2):195-203

Traditional control strategies have difficulty handling nonlinear behavior of structures, time variable features and parameter uncertainties of structural control systems under seismic excitation. An off-and-towardsequilibrium （OTE） strategy combined with fuzzy control is presented in this paper to overcome these difficulties. According to the OTE strategy, the control force is designed from the viewpoint of a mechanical relationship between the motions of the structure, the exciting force and the control force. The advantage of the OTE strategy is that it can be used for a variety of control systems. In order to evaluate the performance of the proposed strategy, the seismic performance of a three-story shear building with an Active Tendon System （ATS） using a Fuzzy Logic Controller （FLC） is studied. The main advantage of the fuzzy controller is its inherent robustness and ability to handle any nonlinear behavior of structures. However, there are no design guidelines to set up the corresponding control rule table for a FLC. Based on the proposed strategy for the FLC, a control rule table associated with the building under study is developed, which then allows formation of a detailed algorithm. The results obtained in this study show that the proposed strategy performs slightly better than the linear quadratic regulator （LQR） strategy, while possessing several advantages over the LQR controller. Consequently, the feasibility and validity of the proposed strategy are verified.  相似文献   

低勘探程度盆地烃源岩早期预测方法研究   总被引：14，自引：1，他引：14  

刘震  常迈  赵阳  李运振  沈怀磊 《地学前缘》2007,14(4):159-167

低勘探领域(深层、深水和新区)是今后油气勘探的重要方向,而有没有有效烃源岩将决定该领域是否具有勘探价值,因此烃源岩评价是低勘探领域早期评价的关键。由于少井条件下烃源岩的评价参数几乎均未知,因此,低勘探程度与烃源岩早期评价是一对矛盾。针对低勘探领域的资料条件,探讨了在层序地层框架基础上的多项烃源岩参数的早期预测及综合评价方法。主要包括4个方面,即(1)层序地层格架分析法确定主力烃源岩层段;(2)地震速度岩性分析法确定烃源岩厚度;(3)烃源岩镜质体反射率地震预测法估算烃源岩成熟度;(4)烃源岩综合评价。本方法充分利用层序地层学方法和地球物理技术,实现了低勘探程度与烃源岩早期评价之间矛盾的转化,成为低勘探领域烃源岩早期预测的一种新方法。  相似文献   

ADCN: An anisotropic density‐based clustering algorithm for discovering spatial point patterns with noise          下载免费PDF全文

Gengchen Mai  Krzysztof Janowicz  Yingjie Hu  Song Gao 《Transactions in GIS》2018,22(1):348-369

Density‐based clustering algorithms such as DBSCAN have been widely used for spatial knowledge discovery as they offer several key advantages compared with other clustering algorithms. They can discover clusters with arbitrary shapes, are robust to noise, and do not require prior knowledge (or estimation) of the number of clusters. The idea of using a scan circle centered at each point with a search radius Eps to find at least MinPts points as a criterion for deriving local density is easily understandable and sufficient for exploring isotropic spatial point patterns. However, there are many cases that cannot be adequately captured this way, particularly if they involve linear features or shapes with a continuously changing density, such as a spiral. In such cases, DBSCAN tends to either create an increasing number of small clusters or add noise points into large clusters. Therefore, in this article, we propose a novel anisotropic density‐based clustering algorithm (ADCN). To motivate our work, we introduce synthetic and real‐world cases that cannot be handled sufficiently by DBSCAN (or OPTICS). We then present our clustering algorithm and test it with a wide range of cases. We demonstrate that our algorithm can perform equally as well as DBSCAN in cases that do not benefit explicitly from an anisotropic perspective, and that it outperforms DBSCAN in cases that do. Finally, we show that our approach has the same time complexity as DBSCAN and OPTICS, namely O(n log n) when using a spatial index and O(n²) otherwise. We provide an implementation and test the runtime over multiple cases.  相似文献