基于DEM的平原区人工微地貌数字提取方法探讨

针对江汉平原区堤垸人工微地貌,综合局部地形分析、水流模拟分析以及GIS空间分析和地统计分析方法,利用SRTM DEM数据进行微地貌自动提取研究。根据人工微地貌特点,构建一种局部地形形态分析方法来对结构线位置进行标示,并提出一种流域合并的方法来进行微地貌结构线提取;进而综合上述两种方法的计算结果,提出平原区人工微地貌的组合提取方法。研究结果表明该方法可较好实现平原区垸堤人工微地貌结构线提取。     

钢筋混凝土梁抗震性能指标分析

采用软件ABAQUS对钢筋混凝土梁进行有限元模拟,即可获取梁的荷载-位移骨架曲线。将试验结果和模拟结果进行对比,结果表明,有限元可以较准确地模拟试验情况。然后同样采用软件ABAQUS来模拟146根梁,并获取该批梁的弯矩-转角骨架曲线。将曲线按照不同因素进行分类,并由这些曲线得出梁的性能参数:塑性转角限值。塑性转角限值能为梁的性能评估提供定量的参考指标。     

河南新乡宋墓家猫骨骼研究

2012年河南新乡市宋墓考古发掘出土一批动物骨骼,根据种属鉴定和观测比较,该批动物骨骼材料属于家猫.家猫(骨骼)安置于墓主身旁,是墓主入葬时作为饲宠特意放置的.猫骨骼表面没有发现任何人类行为痕迹(切割、砍击等).全部猫骨骼属于同一个家猫个体.保存下来的骨骼材料包括左、右下颌骨;左上颌骨;肱骨、尺骨、桡骨、股骨、胫骨、跖骨等,总计42件家猫骨骼.在家猫动物考古研究中,新乡宋墓家猫是我国同一地点发现家猫骨骼标本数(可鉴定标本数:NISP)最多的地点.特别需要关注的是,在该具家猫骨骼上,首次发现我国家畜考古中"偏侧咀嚼"现象.其特征为:右下颌的P4、m1齿尖,使用磨耗程度远远大于左下颌相同齿位齿尖.磨耗差距最大的部位在m1后尖顶端,右侧比左侧齿尖因磨耗而偏低2.10 mm,右侧m1后尖顶端已磨耗为平面、裸露齿质点,而左侧m1齿尖仍保留有完好锐尖.新乡宋墓家猫在我国动物考古中,还是首次发现以宠物猫进行陪葬的考古学文化现象.我国此前发现的家猫骨骼,主要出土于文化层或灰坑里,可能是被人们丢弃或自然死亡后被埋藏起来的.甚至还有少量猫骨可能是古代人食猫风俗的遗存.而新乡宋墓中的宠物猫,是人们为培养生活伴侣或寄托生活情趣而畜养的,是人们主要为满足精神生活需求而饲养的动物.我国此前动物考古研究有关"宠物"的发现为空白.新乡宋墓出土我国考古中第一只可以确定为宠物的家猫,为今后开展动物考古中有关"宠物"研究开启了良好开端.墓中出土的宠物猫还有严重"偏侧咀嚼"现象,该发现对家畜动物考古材料的演化研究等具有重要意义.     

准噶尔盆地玛6井区侏罗系三工河组S22砂层地震相分析

现代新技术手段是克服地震资料解释多解性的重要方法。作者在本文中以三维地震资料为基础，运用Stratimagic地震相分析以及振幅切片等技术手段，对准尔盆地玛6井区侏罗系三工河组S2^2砂体展布进行了全面分析，识别出研究目的层段骨架砂体的平面展布特征，并进一步结合地震剖面的反射结构特征，展开精细的地震相研究。研究结果发现，玛6井区三江河组S2^2砂层主要为一个三角洲沉积。     

A New Giant Compsognathid Dinosaur with Long Filamentous Integuments from Lower Cretaceous of Northeastern China

1 Introduction Compsognathids are a small group of theropods commonly placed at the basal position within Coelurosauria (Sereno, 1999; Rauhut, 2003; Holtz and Osmólska, 2004; Norell and Xu, 2005). Recently new findings make the number of valid compsognathid genera increase rapidly. This group contains the relatively complete Compsoganthus (Ostrom, 1978; Bidar et al., 1972) and Juravenator (G?hlich and Chiappe, 2006) from the Upper Jurassic of West Europe, and Sinosauropteryx (Ji and J…     

Hybrid time integration and coupled solution methods for nonlinear finite element analysis of partially saturated deformable porous media at small strain

The goal of the paper is to determine the most efficient, yet accurate and stable, finite element nonlinear solution method for analysis of partially saturated deformable porous media at small strain. This involves a comparison between fully implicit, semi‐implicit, and explicit time integration schemes, with monolithically coupled and staggered‐coupled nonlinear solution methods and the hybrid combination thereof. The pore air pressure p_a is assumed atmospheric, that is, p_a=0 at reference pressure. The solid skeleton is assumed to be pressure‐sensitive nonlinear isotropic elastic. Coupled partially saturated ‘consolidation’ in the presence of surface infiltration and traction is simulated for a simple one‐dimensional uniaxial strain example and a more complicated plane strain slope example with gravity loading. Three mixed plane strain quadrilateral elements are considered: (i) Q4P4; (ii) stabilized Q4P4S; and (iii) Q9P4; “Q” refers to the number of solid skeleton displacement nodes, and “P” refers to the number of pore fluid pressure nodes. The verification of the implementation against an analytical solution for partially saturated pore water flow (no solid skeleton deformation) and comparison between the three time integration schemes (fully implicit, semi‐implicit, and explicit) are presented. It is observed that one of the staggered‐coupled semi‐implicit schemes (SIS(b)), combined with the fully implicit monolithically coupled scheme to resolve sharp transients, is the most efficient computationally. Copyright © 2015 John Wiley & Sons, Ltd.     

A constitutive model for unsaturated soil–structure interfaces

A constitutive model for simulation of the behavior of unsaturated interfaces is presented here. The model is an extension of an existing critical state compatible interface model for dry and saturated interfaces that was already proposed by one of the authors [Lashkari, A. 2013. Int. J. Numer. Anal. Meth. Geomech. 37 (8): 904–931]. For a proper simulation of the behavior of partially saturated interfaces, the extended model is formulated in terms of two pairs of work conjugate stress–strain‐like variables. The modified model simulations are compared with the existing data of dry, unsaturated, and saturated interfaces. For each interface type, it is shown that the proposed model can capture the essential elements of the behavior using a unique set of parameters. Copyright © 2015 John Wiley & Sons, Ltd.     

以弯曲骨架线为化简指标的海岸线综合方法

针对海岸线综合中以弯曲高度和弯曲深度为化简指标的不足,提出了以弯曲骨架线为指标的综合方法。在基于曲线单调段的弯曲识别的基础上,通过弯曲部位三角网的构建提取了弯曲骨架线。结合＂扩陆缩海＂原则进行了海岸线综合实验,验证了该方法在保持海岸线形态特征方面的有效性与可行性。     

地形特征线提取方法的研究进展

地形与地貌是数字地形分析中重要的自然地理要素,数字高程模型中蕴含着丰富的地形地貌信息,从中提取地形特征线信息是当前地学研究的热点之一。目前,很多学者使用不同的方法来研究地形特征线的提取,但是仍然存在着许多不足之处。本文对这些方法进行了介绍,对各种方法的研究现状展开综述并分析了优点和不足,最后对特征线提取方法存在的主要问题进行总结和展望。     

3D tree modeling from incomplete point clouds via optimization and L1-MST

Reconstruction of 3D trees from incomplete point clouds is a challenging issue due to their large variety and natural geometric complexity. In this paper, we develop a novel method to effectively model trees from a single laser scan. First, coarse tree skeletons are extracted by utilizing the L₁-median skeleton to compute the dominant direction of each point and the local point density of the point cloud. Then we propose a data completion scheme that guides the compensation for missing data. It is an iterative optimization process based on the dominant direction of each point and local point density. Finally, we present a L₁-minimum spanning tree (MST) algorithm to refine tree skeletons from the optimized point cloud, which integrates the advantages of both L₁-median skeleton and MST algorithms. The proposed method has been validated on various point clouds captured from single laser scans. The experiment results demonstrate the effectiveness and robustness of our method for coping with complex shapes of branching structures and occlusions.