Estimating fractal dimension of lineaments using box counting method for the Indian landmass     

V. Jaya  S. Sonika Mohan 《国际地球制图》2013,28(3):314-331

A fractal in general is a scale-invariant object that has an underlying power-law equation and is characterized by a positive fractal dimension. The fractal dimension of the Indian landmass is evaluated from the lineament map by utilizing the MATLAB programme for box counting method. The lineament map of India is divided into grids. The fractal dimension of each grid is obtained and the values are mapped. Most of the regions of India has fractal dimension in the range 1–1.25. The fractal values are compared with b-value in Gutenberg–Richter equation which gives a relationship between frequency of occurrence of earthquake and its magnitude. The estimation of b-value requires a complete earthquake dataset. In regions where the complete earthquake data are not available, the fractal dimension evaluated from the study can be used as a parameter to assess the seismic hazard of the region.  相似文献   

Discrimination of reworked pyroclastics from primary tephra-fall tuffs: a case study using kimberlites of Fort a la Corne, Saskatchewan, Canada     

Kevin Leahy 《Bulletin of Volcanology》1997,59(1):65-71

 Reworked volcaniclastics are traditionally discriminated from primary tephra-fall pyroclastics by an absence of features such as blanketing, juvenile lapilli, grain welding and poor sorting. Frequently, these features are difficult to identify, especially in small outcrops, ancient or altered successions, debris flows and surge deposits. Crystal-rich volcaniclastics, such as kimberlites, have a large proportion of coarse euhedral crystals, and abrasion leading to rounding can be recognised and classified with relative ease. A petrographic method of discriminating reworked material has been devised, based on the degree of grain roundness, and is illustrated using volcaniclastic kimberlite from Fort a la Corne, Saskatchewan, Canada. Petrographic thin sections of samples at regular intervals throughout the borehole core, and from a nearby crater-facies kimberlite, show that the percentages of rounded, subrounded and euhedral grains define two distinct groupings. The first group contains a higher percentage of euhedral grains and includes all the samples from the basal 4.8 m of the 14.1-m-thick kimberlite section in borehole 004, and all of the crater facies tephra-fall tuffs. A second group contains more rounded, subrounded and fragmental grains and includes all the data from the upper 6.3 m, which are interpreted as reworked strata. Thus, point counting concurs with hand-sample interpretation and may be used as a verification tool in discriminating reworked pyroclastic sands from primary tephra-fall tuffs. Received: 27 August 1996 / Accepted: 31 May 1997  相似文献   

Scale Transitions in Fracture and Active Fault Networks     

Thomas H. Wilson 《Mathematical Geology》2001,33(5):591-613

Detailed box counting analysis was conducted of (1) fractures observed in exposures of the Devonian Shale in the central Appalachians Valley and Ridge Province of West Virginia, (2) several fracture patterns presented in the literature, and (3) active faults mapped throughout the main island (Honshu) of Japan. Box curves reveal, with few exceptions, that most naturally occurring fracture patterns are characterized by nonfractal behavior. In many cases, two linear regions separated by an abrupt transition are observed in the logN/logr box curves. The small-scale (larger r) features generally have higher fractal dimension than do the larger scale features in the pattern. Transitions from one region to another are usually abrupt. These transitions are not associated with sampling problems or other data limitations. In some cases three or more linear regions may appear. Box counting analysis of model fracture patterns indicate that transitions are related to the dominant spacing of individual sets or to the dominant fragment size in the network. This study provides detailed documentation of scale invariant features in natural fracture and active fault patterns. Although the relationship of the geometrical properties of a pattern to the location of transitions is understood in terms of the models, to understand the physical mechanisms responsible for these transitions deserves further study.  相似文献   

An improvement in the small-volume technique for determining thorium-234 in seawater   总被引：3，自引：0，他引：3  

Pinghe Cai  Minhan Dai  Dongwei Lv  Weifang Chen 《Marine Chemistry》2006,100(3-4):282

The recently developed 2–5 L small-volume MnO₂ coprecipitation method for determining ²³⁴Th in seawater has provided a new way to substantially increase, both temporally and spatially, the sampling resolution of ²³⁴Th and ²³⁴Th-based particulate organic carbon export estimates in the upper ocean. In this study, we further optimize the technique by reducing reagent quantities and the use of an additional water bath heating step. This optimization allows the filtration of the MnO₂ precipitate onto a 25-mm diameter, 1.0 μm pore size QMA filter to be completed within < 30 min for unfiltered waters from the South China Sea. In addition, we have modified the MnO₂ purification procedure to allow for alpha spectrometric measurements of ²³⁴Th recoveries. Results from recovery experiments suggest that reagent amounts can be reduced to 0.0375 mg KMnO₄ and 0.1 mg MnCl₂·4H₂O per liter of sample, while still maintaining high ²³⁴Th recovery. This study further confirms that the addition of a yield monitor is necessary for the application of the small-volume method.  相似文献   

基于实测应力的半潜平台疲劳损伤分析     

武博  王璞  李欣  杨建民 《海洋工程》2020,38(2):17-26

疲劳破坏是海洋结构物发生破坏的一种主要形式,深水半潜平台在海上运输、作业、停滞时会受到交变的风、浪、流载荷作用,进而引起结构关键节点处的疲劳损伤,影响平台安全性。以"海洋石油981"半潜钻井平台为研究对象,利用光纤光栅应变传感器对结构高应力区进行应力监测,获取测点处应力时历数据。将监测位置划分为四个监测板块,采用四点雨流计数法对测点应力进行处理,得到以离散形式给出的应力循环幅度与相应循环周次。参照DNV《海上钢结构疲劳设计规范》推荐的S-N曲线,基于Miner线性疲劳累计损伤原则,得到各个测点处的总体疲劳损伤度。选取具有最大疲劳损伤度的危险测点,并结合海上实测总时长,预测半潜平台的总体疲劳寿命。  相似文献   

A split-beam echo-counting model for riverine use     

Mulligan  Timothy J.; Kieser  Robert 《ICES Journal of Marine Science》1996,53(2):403-406

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由主厂房建立建筑坐标系统方法的研究     

奚毓敏 《现代测绘》2003,26(4):18-21

本文对由主厂房建立建筑坐标系统方法进行归纳总结，对应用中应引起重视的技术问题进行了深入研究，并给出了解决方案，这对提高精度和防止出错是非常重要的。同时指出极坐标方法二中的计算错误所在及其本质，应停止使用。  相似文献   

云南天文台新型斑点象探测系统   总被引：1，自引：0，他引：1  

卢汝为  王锋  楼柯  邱耀辉  刘忠 《天文研究与技术》1998,(1)

斑点成象技术能有效地消除地球大气湍流的不良影响,实现地基大型天文望远镜的衍射受限分辨率成象,其所需的原始数据是天文目标及参考星的一系列的短曝光斑点象,它们取自望远镜的终端设备：斑点象探测系统。文中对比该技术对原始数据的要求：介绍了云南天文台研制的新型斑点象探测系统的结构和性能。实际观测结果表明,该系统基本能满足要求。  相似文献   

Counting chronology and climate records with about 1000 annual layers of a Holocene stalagmite from the Water Cave in Liaoning Province, Chinaannual layers of a Holocene stalagmite from the Water Cave in Liaoning Province, China     

Juzhi Hou  Ming Tan  Dongsheng Liu 《中国科学D辑(英文版)》2002,45(5):385-391

One active stalagmite from the Water Cave in Liaoning Province contains growth layers of three sizes. Based on thermal ionization mass spectrometry ²³⁰Th dating, we found that middle size layers are annual layers, with each middle layer consisting of one narrow dark layer and a wide bright layer. The small layers within middle layers are sub-annual layers and the large layers are multi-year layers. Based on the layer-counting method, we established a high-resolution time scale for layer thickness. Our results reveal two dramatic century-scale climate cycles over the past 1000 years in this region.  相似文献   

Pebble and Sandstone Compositions and Provenance Analysis of the Upper Cretaceous Hekou Formation of Yongfeng-Chongren Basin, Jiangxi, SE China     

CHEN Liuqin  GUO Fusheng  LIANG Wei 《《地质学报》英文版》2013,87(Z1):536-538

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