Lack of mitochondrial genetic structure in the endangered giant clam populations of Tridacna maxima (Bivalvia: Cardiidae: Tridacninae) across the Saudi Arabian coast     

Ben Othmen Abdelwahe  Abhary Mohame  Deli Temim  Ouanes Zouhour  Alhuwaiti Nour  Dimassi Najet  Mansour Lamjed 《海洋学报(英文版)》2020,39(2):28-37

The present investigation focuses on population genetic structure analysis of the endangered giant clam species Tridacna maxima across part of the Red Sea,with the main aim of assessing the influence of postulated potential barriers to gene flow(i.e.,particular oceanographic features and marked environmental heterogeneity)on genetic connectivity among populations of this poorly dispersive bivalve species.For this purpose,a total of 44 specimens of T.maxima were collected from five sampling locations along the Saudi Arabian coast and examined for genetic variability at the considerably variable mitochondrial gene cytochrome c oxidase I(COI).Our results revealed lack of population subdivision and phylogeographic structure across the surveyed geographic spectrum,suggesting that neither the short pelagic larval dispersal nor the various postulated barriers to gene flow in the Red Sea can trigger the onset of marked genetic differentiation in T.maxima.Furthermore,the discerned shallow COI haplotype genealogy(exhibiting high haplotype diversity and low nucleotide diversity),associated with recent demographic and spatial expansion events,can be considered as residual effect of a recent evolutionary history of the species in the Red Sea.  相似文献   

板876地下储气库水砂体评价与扩容利用     

谢俊  潘芝平  王亚洲  梁会珍  王皆明  王金凯 《中国海洋大学学报(自然科学版)》2020,(2):100-106

由常规枯竭型气藏改建的地下储气库仍然以气藏砂体(气砂体)为研究目标,与气藏砂体相邻的含水层(水砂体)亦能作为地下储气库的扩容空间,但这部分砂体很少被关注。板876地下储气库在储层精细描述基础上,结合气藏和气库的注采动、静态分析结果,评价了水砂体的分布范围和发育规模,利用精细地质模型计算了水砂体的总孔隙体积、未动用的及可动用的孔隙体积,应用板876地下储气库数值模拟技术对水砂体的扩容空间进行了验证,结果表明水砂体储集空间对地下储气库的扩容和运行效率具有现实意义。  相似文献   

Efficient sparse polynomial chaos expansion methodology for the probabilistic analysis of computationally‐expensive deterministic models     

T. Al‐Bittar  A.‐H. Soubra 《国际地质力学数值与分析法杂志》2014,38(12):1211-1230

The sparse polynomial chaos expansion (SPCE) methodology is an efficient approach that deals with uncertainties propagation in case of high‐dimensional problems (i.e., when a large number of random variables is involved). This methodology significantly reduces the computational cost with respect to the classical full PCE methodology. Notice however that when dealing with computationally‐expensive deterministic models, the time cost remains important even with the use of the SPCE. In this paper, an efficient combined use of the SPCE methodology and the Global Sensitivity Analysis is proposed to solve such problem. The proposed methodology is firstly validated using a relatively non‐expensive deterministic model that involves the computation of the PDF of the ultimate bearing capacity of a strip footing resting on a weightless spatially varying soil where the soil cohesion and angle of internal friction are modeled by two anisotropic non‐Gaussian cross‐correlated random fields. This methodology is then applied to an expensive model that considers the case of a ponderable soil. A brief parametric study is presented in this case to show the efficiency of the proposed methodology. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Bearing capacity of strip footings on spatially random soils using sparse polynomial chaos expansion     

Tamara Al‐Bittar  Abdul‐Hamid Soubra 《国际地质力学数值与分析法杂志》2013,37(13):2039-2060

A probabilistic model is presented to compute the probability density function (PDF) of the ultimate bearing capacity of a strip footing resting on a spatially varying soil. The soil cohesion and friction angle were considered as two anisotropic cross‐correlated non‐Gaussian random fields. The deterministic model was based on numerical simulations. An efficient uncertainty propagation methodology that makes use of a non‐intrusive approach to build up a sparse polynomial chaos expansion for the system response was employed. The probabilistic numerical results were presented in the case of a weightless soil. Sobol indices have shown that the variability of the ultimate bearing capacity is mainly due to the soil cohesion. An increase in the coefficient of variation of a soil parameter (c or φ) increases its Sobol index, this increase being more significant for the friction angle. The negative correlation between the soil shear strength parameters decreases the response variability. The variability of the ultimate bearing capacity increases with the increase in the coefficients of variation of the random fields, the increase being more significant for the cohesion parameter. The decrease in the autocorrelation distances may lead to a smaller variability of the ultimate bearing capacity. Finally, the probabilistic mean value of the ultimate bearing capacity presents a minimum. This minimum is obtained in the isotropic case when the autocorrelation distance is nearly equal to the footing breadth. However, for the anisotropic case, this minimum is obtained at a given value of the ratio between the horizontal and vertical autocorrelation distances. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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胡守超  伍吉仓  孙亚峰 《大地测量与地球动力学》2009,29(3):95-99

????(Stacking)??????????????PCA????Karhunen??Loeve???(KLE)??3?????????????????????????12??GPS????????5?????????????С?????????3???????????Ч???????????????????д????????????????????????????????????????÷?Χ???в????  相似文献   

基于GIS城镇空间扩展的评价研究——以来安汊河新区为例     

胡明星  权亚玲 《四川测绘》2009,32(5):195-199

通过对来安汉河新区总体概念规划的实践，本文在新区空间扩展评定中建立了评价分类的指标体系、确定了指标因子分级，并采用特尔斐法和层次分析法相结合的方法计算出评价指标因子权重值。在此基础上采用多因子综合评价方法，在GIS数据库中计算出每个单元的综合评价值，并依据该值进行等级划分，评定出汉河新区空间扩展范围和具体位置，为新区空间扩展的规划提供了科学根据。  相似文献   

Gravity Anomaly Calculation Based on Volume Integral in Spherical Cap and Comparison with the Tesseroid-Taylor Series Expansion ApDroach     

《测绘学报》2012,41(3)

利用重力资料研究区域乃至全球地质问题时,重力或重力异常正演方法最好从基于直角坐标系向球坐标系方向发展。本文对近似的球冠面积分重力异常正演方法进行改进,使其计算精度和计算效率都得到很大程度地提高;再通过数值试验及实际应用,分析Tesseroid单元体基于泰勒级数展开的重力正演方法与球冠重力正演方法的计算精度与稳定性,最后探讨两种方法的优缺点及其应用方向。  相似文献   

烟台市城市群空间扩展特征分析     

孙云华  张安定  王庆  衣华鹏 《测绘科学》2012,37(3):69-71,146

准确判别城市扩展规律、剖析演化过程,对于预测城市未来演化趋势、制定合理的调控政策具有重要的意义。本文以1989年TM、2000年ETM+、2009年TM影像为依据,应用RS和GIS手段提取了山东半岛北部烟台市城市群的实体边界,分析了烟台地区1989年-2009年间城市扩展的面积、方向以及城市扩展的导向规律。研究结果表明:烟台市城市群在近20年一直处于城市扩展的快速发展阶段,并受到地形、临港产业、交通干线以及政府调控等方面的影响。  相似文献   

曲面边坡建模及展开的方法     

黄海丽  李浩  王淼 《测绘科学》2012,37(6):138-139,143

工程边坡作为水利水电、矿山运输等工程中最为常见的地质形态,是地质编录中主要的处理对象。现今的地质编录对于平面边坡已经能够很好地解决并生成正射影像,但对曲面边坡的建模与展示研究还比较少。本文给出一种基于斜轴圆柱曲面边坡建模的方法,并将影像投射到展示平面上生成正射影像。实践表明,建模方法实用、快捷,模型展开方法较简单,精度符合地质编录要求。  相似文献   

Driving forces of ＂poplar expansion and cropland shrinkage＂ in the North China Plain：A case study of Wen＇an County,Hebei Province     

《地理研究》2012,31(2)

以Landsat5TM遥感影像、农户调查数据和统计数据为基础数据,运用3S技术提取了案例区河北省文安县1995～2007年土地利用变化信息,分析了杨树扩张的时空格局;并从农户杨树种植决策行为视角,运用数理统计、投入产出法分析了杨树扩张占地的驱动因素。结论如下：（1）杨树林地扩张幅度大、速率快。（2）杨树扩张所用土地92.14%来源于耕地,＂杨上粮下＂现象突出。（3）杨树扩张速率的空间差异显著。杨树扩张受生产要素、土地产品市场及政策因素的综合驱动,其中劳动力因素和经济因素起主要作用。（4）非农从业人员比率和农民年人均收入越高,杨树扩张速度越快。在劳动力由富余转为相对稀缺的情况下,农户为提高经济收益,倾向选择耗工少,劳动生产率较大的杨树,是杨树扩张占地的根本原因。  相似文献