The missing Myopus: plugging the gaps in Late Pleistocene small mammal identification in western Europe with geometric morphometrics

Lemmus and Myopus are two lemming species with distinct habitat requirements but which show very similar dental morphologies. They are thus extremely difficult to distinguish from one another in the fossil record on the basis of their dental remains, leading to poor understanding of the palaeobiogeographical evolution of Myopus as well as inaccurate palaeoenvrionmental reconstructions. Currently, the presence of Myopus in the fossil register from the Pleistocene is still debated and no firm occurrence of this lemming in western Europe has yet been confirmed for the Late Pleistocene. In this paper, we used geometric morphometrics on modern material to establish morphological differences between Lemmus and Myopus teeth (first lower and third upper molars). Morphological data were then used to build a robust linear discriminant model able to confidently classify isolated teeth of these two genera, and finally, linear discriminant models were used on fossil remains of Lemmus/Myopus from two Late Pleistocene archaeological/palaeontological sites (Grotte des Gorges and Gully Cave). This study demonstrates, for the first time, the presence of Myopus schisticolor in west European Late Pleistocene sites between the end of Marine Isotope Stage 3 and the beginning of the Holocene, during climatic events that favoured the development of taiga forest of birch and pine in these regions.     

饱和层状场地中任意凹陷地形对入射SV波的散射

利用饱和土层的精确动力刚度矩阵和动力格林(Green)函数,采用间接边界元法,在频域内求解了层状饱和场地中任意凹陷地形对入射SV波的散射问题.通过自由场反应分析,求得凹陷地形表面各点的位移和各单元的应力响应;同样计算了虚拟分布荷载的格林影响函数,求得相应的位移和应力响应;根据边界条件确定虚拟分布荷载,将自由场位移响应和...     

安装形状记忆合金阻尼器的剪力墙结构抗震性能分析

为减轻钢筋混凝土剪力墙连梁的地震后永久性损伤,同时保持连梁的耗能机制,本文提出在剪力墙连梁中安装新型形状记忆合金(Shape Memory Alloy,简称SMA)阻尼器,并研究该阻尼器对剪力墙结构地震响应的减震效果。通过一幢12层剪力墙结构地震反应的时程分析,研究了SMA阻尼器的附加刚度比和屈服位移比两项特征参数对结构地震反应控制效果的影响规律。计算分析结果表明,当附加刚度比为0.04～0.05,屈服位移比为0.4～0.5时,可以获得较好的减震效果。     

结构参数对双链式悬索桥地震响应的影响

以某双链式悬索桥为工程背景,建立了空间有限元计算模型.运用几何非线性时程分析方法,分析并探讨了不同垂跨比、阻尼比,塔桥不同连接方式和双链位置对双链式悬索桥地震响应的影响.分析表明,竖向地震动分量使桥塔轴力迅速增大,加劲梁采用钢筋混凝土边梁可有效减小地震响应;塔梁间采用简支连接方案其抗震性能比固定支座连接方案、滑动支座连接方案要好;双链式悬索桥横向抗震性能优于单链式悬索桥.对双链式悬索桥抗震性能的研究,为此类悬索结构的设计选型,乃至减震、隔震及抗震加固提供了参考.     

利用NSCT和Krawtchouk矩进行图像检索

提出了一种基于非下采样Contourlet变换(nonsubsampled contourlet transform,NSCT)和Krawtchouk矩的图像检索算法。首先,通过NSCT对图像进行分解,提取每个分解层次上不同方向子带系数分布的数学特征作为图像的纹理特征;然后,利用Krawtchouk矩描述图像的形状特征;最后,根据加权的相似性度量实现图像检索。实验结果表明,所提取的特征向量具有平移、旋转、尺度不变性,且能获得更高的检索精度。     

利用几何矩和叠置分析进行多尺度面要素自动匹配

针对地图中重要的面要素的自动匹配问题进行了研究。由于在实际情况中,多尺度同名面要素在位置上可能偏差较大,又存在非一对一的匹配关系,现有的方法均难以进行有效匹配。为解决这个问题,首先提取面要素的全局形状特征,并给出了一种快速获取候选匹配面要素组合的方法,然后利用几何矩获取面要素组合的质心,在将待匹配面要素与组合面要素的质心相互重合后,通过计算重叠相似度来判定多尺度面要素之间的匹配关系。实验表明,本文方法即使在同名面要素存在较大位置偏差,甚至非均匀位置偏差时,仍可有效地处理面要素的一对一和一对多两种匹配关系,从而拓展了面要素匹配方法的适用范围,降低了对外界条件的要求和限制。     

Computing Streamfunction and Velocity Potential in a Limited Domain of Arbitrary Shape. Part I: Theory and Integral Formulae

The non-uniqueness of solution and compatibility between the coupled boundary conditions in computing velocity potential and streamfunction from horizontal velocity in a limited domain of arbitrary shape are revisited theoretically with rigorous mathematic treatments.Classic integral formulas and their variants are used to formulate solutions for the coupled problems.In the absence of data holes,the total solution is the sum of two integral solutions.One is the internally induced solution produced purely and uniquely by the domain internal divergence and vorticity,and its two components(velocity potential and streamfunction) can be constructed by applying Green’s function for Poisson equation in unbounded domain to the divergence and vorticity inside the domain.The other is the externally induced solution produced purely but non-uniquely by the domain external divergence and vorticity,and the non-uniqueness is caused by the harmonic nature of the solution and the unknown divergence and vorticity distributions outside the domain.By setting either the velocity potential(or streamfunction) component to zero,the other component of the externally induced solution can be expressed by the imaginary(or real) part of the Cauchy integral constructed using the coupled boundary conditions and solvability conditions that exclude the internally induced solution.The streamfunction(or velocity potential) for the externally induced solution can also be expressed by the boundary integral of a double-layer(or singlelayer) density function.In the presence of data holes,the total solution includes a data-hole-induced solution in addition to the above internally and externally induced solutions.     

几种统计相似方法的适用性比较

针对前人对各种相似性度量的预报检验结果,从公式出发,分析证明了相似离度与海明距离具有相同性质,探讨了相似离度在相似预报中使用的局限性。利用2010年5月1—30日08时东亚区域850 hPa高度场96个站点资料,对几个常用相似量及作者提出的新相似量进行相似选择试验,结果表明：（1）相似离度与海明距离非常接近,选出的相似样本80%以上是相同的;（2）相似离度与相关系数差异最大,选出的相似样本70%以上是不同的;（3）新相似量与相关系数较接近,60%是相同的。相似离度与海明距离反映的是样本间＂距离＂的接近程度,相关系数和新相似量反映的是样本间的形状接近程度。     

树冠形状对孔隙率及叶面积指数估算的影响分析

叶片在树冠尺度的聚集是森林场景中的重要聚集形式,模型中常假设树冠为规则的几何形体(椭球、圆锥、圆锥+圆柱等)。对树冠形状归属进行判断时界限并不明显,从而具有很强的主观性。本文首先扩展了Nilson的森林孔隙率模型,使其适用于椭球、圆锥、圆锥+圆柱等3种常见形状的树冠,并基于该模型分析了孔隙率、聚集指数对树冠形状的敏感性。同时,本文还分析了树冠形状对叶面积指数(LAI)地面间接测量精度的影响。基于不同形状树冠的模拟数据分析发现,树冠的体积、投影面积是树冠形状产生作用的主要因子,在冠层底部椭球形树冠和圆锥+圆柱形树冠的平均孔隙率、聚集指数都非常接近,而圆锥形树冠与两者存在较大差异。树冠形状的错误设置在极端情况下可导致估算的真实LAI误差超过25%。     

高分辨率遥感影像目标形状特征多尺度描述与识别

在高分遥感影像中,同类地物目标形状具有多样性,单一尺度或单一形状模版不足以描述同类目标的形状。本文利用小波变换和Fourier描述子构建了一种目标形状的多尺度描述模型,并基于该模型给出了一种新的面向对象的高分遥感影像目标识别方法。从上到下,该模型采用尺度依次减小的小波近似系数对原始形状进行近似表示,并利用Fourier描述子对其进行定量描述。利用语义规则综合考虑多个尺度下的识别结果,得到最终识别结果,减小小尺度下分割目标破碎和大尺度下小目标无法识别造成的影响,提高识别精度。基于本文方法分别对高分遥感影像中的飞机和建筑物进行识别,对比实验表明,该方法具有较高识别精度。