Stochastic simulation of patterns using Bayesian pattern modeling

In this paper, a Bayesian framework is introduced for pattern modeling and multiple point statistics simulation. The method presented here is a generalized clustering-based method where the patterns can live on a hyper-plane of very low dimensionality in each cluster. The provided generalizationallows a remarkable increase in variability of the model and a significant reduction in the number of necessary clusters for pattern modeling which leads to more computational efficiency compared with clustering-based methods. The Bayesian model employed here is a nonlinear model which is composed of a mixture of linear models. Therefore, the model is stronger than linear models for data modeling and computationally more effective than nonlinear models. Furthermore, the model allows us to extract features from incomplete patterns and to compare patterns in feature space instead of spatial domain. Due to the lower dimensionality of feature space, comparison in feature space results in more computational efficiency as well. Despite most of the previously employed methods, the feature extraction filters employed here are customized for each training image (TI). This causes the features to be more informative and useful. Using a fully Bayesian model, the method does not require extensive parameter setting and tunes its parameters itself in a principled manner. Extensive experiments on different TIs (either continuous or categorical) show that the proposed method is capable of better reproduction of complex geostatistical patterns compared with other clustering-based methods using a very limited number of clusters.     

Holocene changes on a peatland in northwestern Ontario interpreted from testate amoebae (Protozoa) analysis

Radiocarbon-dating and analyses of fossil testate amoebae (Protozoa) have established changes in soil moisture conditions on the developing surface of a Sphagnum -dominated peatland near Emo in northwestern Ontario.
The distribution and composition of modern testate amoebae communities were studied from peatlands in the region of Ontario and Minnesota as a guide to interpreting fossil assemblages. Although the core spans all of the Holocene, fossil testate amoebae were recovered only from the part post-dating 6500 BP. Earliest testate amoebae assemblages associated with bryophytic and cyperaceous-rich fen peat are dominated by species in the genera Cyclopyxis and Centropyxis . By 5000 BP, Amphitrema Jraaum, Assulina muscorum, Heleopera sphugni and Hyalosphenia subjaoa become important species as Sphagnum-rich peat accumulated at the site. Present-day microtopographic differentiation probably developed during historic time when the site became progressively drier, as indicated by a change of Nebela griseola, N. militaris and Trigonopyxis arcula . Although it is possible to derive quantitative estimates of changing soil moisture conditions from testate amoebae, care should be taken in interpreting results, particularly from non-Sphagnum-rich peats, until more is learned about the distribution and ecology of modern faunas.     

Controlled moraines: origins,characteristics and palaeoglaciological implications

Controlled moraines are supraglacial debris concentrations that become hummocky moraine upon de-icing and possess clear linearity due to the inheritance of the former pattern of debris-rich folia in the parent ice. Linearity is most striking wherever glacier ice cores still exist but it increasingly deteriorates with progressive melt-out. As a result, moraine linearity has a low preservation potential in deglaciated terrains but hummocky moraine tracts previously interpreted as evidence of areal stagnation may instead record receding polythermal glacier margins in which debris-rich ice was concentrated in frozen toe zones. Recent applications of modern glaciological analogues to palaeoglaciological reconstructions have implied that: (a) controlled moraine development can be ascribed to a specific process (e.g. englacial thrusting or supercooling); and (b) controlled moraine preservation potential is good enough to imply the occurrence of the specific process in former glacier snouts (e.g. ancient polythermal or supercooled snouts). These assumptions are tested using case studies of controlled moraine construction in which a wide range of debris entrainment and debris-rich ice thickening mechanisms are seen to produce the same geomorphic features. Polythermal conditions are crucial to the concentration of supraglacial debris and controlled moraines in glacier snouts via processes that are most effective at the glacier–permafrost interface. End moraines lie on a process–form continuum constrained by basal thermal regime. The morphological expression of englacial structures in controlled moraine ridges is most striking while the moraines retain ice cores, but the final deposits/landforms tend to consist of discontinuous transverse ridges with intervening hummocks, preserving only a weak impression of the former englacial structure. These are arranged in arcuate zones of hummocky moraine up to 2 km wide containing ice-walled lake plains and lying down flow of streamlined landforms produced by warm-based ice. A variety of debris entrainment mechanisms can produce the same geomorphic signature. Spatial and temporal variability in process–form relationships will lead to the sequential development of different types of end moraines during the recession of a glacier or ice sheet margin.     

Isotopic constraints on the Easter Seamount Chain source

New isotopic data (Sr, Nd and Pb) for lavas from Easter and Salas y Gomez Islands, and nine seamounts along the length of the Easter Seamount Chain (ESC) to the east of these islands, exhibit a regular behavior that is consistent with two-component mixing between a MORB-like source and more enriched mantle (the Easter Plume source) characterized by relatively radiogenic Pb and unradiogenic Sr. Based on the linearity of mixing trends on the isotope diagrams, the plume source appears to have maintained approximately the same isotopic composition over the 20 to 30 Ma history of the Easter Plume sampled by the seamounts. In current nomenclature, the plume source resembles a mix of predominantly HIMU mantle with a small amount of EMI. The proportions of MORB and plume source mantle sampled by the lavas erupted along the ESC vary in a systematic way, with Easter Island and seamounts to the west containing larger fractions of the MORB component than Salas y Gomez Island and the older seamounts to the east. This variability is probably a reflection of the nearness to the spreading center, and therefore lithospheric thickness, at the time of volcanism Received: 27 April 1998 / Accepted: 11 December 1998     

上部地壳的流体作用与大理岩的低温塑性

本文应用光学显微镜、透射电子显微镜和阴极发光显微镜系统研究了Ｗａｔｅｒｂｅｒｇ断层带（纳米比亚）内粗晶大理岩中发育的构造岩,宏观碎裂结构与微观糜棱装结构是断层构造岩的主要特点。巨大的孪形碎屑与弥漫的细小粒质形成了鲜明的反差,广泛发育的压溶颖合线与多阶段方解石细脉遍布构造带不同部位,ＴＥＭ亚微粒粒度具有简单的峰值分布（～０．３～０．４μｍ）,但动态重结晶颗粒的粒度却具有较大的变化范围（０．１～３．０     

泰国东北呵叻府苏拉娜里地区新生代硅化木及其古环境意义

摘要: 泰国东北部新生代硅化木十分丰富且保存完好。经对23 件木化石标本研究,已鉴定出真双子叶植物6 科7 属约13 种,包括Canarium sp． ( Burseraceae) ; Terminalia sp． vel Combretum sp． ,Terminalia sp． ( Combretaceae) ; cf． Irvingia sp． ( Irvingiaceae) ; Cynometroxylon holdeni,Cynometroxylon sp． ,cf． Cynometroxylon spp． ,cf． Millettia spp． ( Leguminosae) ; Careya spp. ( Lecythidaceae) ; Azadirachta sp． ( Meliaceae) ; 以及其他4 个分类群( 分类位置待定) 。这些高度分化的古植物群显示出与泰国东北部现存的混合落叶林、干旱阔叶林和干旱常绿林非常相似的特征,反映了该地区当时的古气候是近于湿润的热带疏林草原气候( 热带干湿气候) 。     

Particle manifold method (PMM): A new continuum‐discontinuum numerical model for geomechanics

Particle manifold method (PMM) is a new extension of the numerical manifold method (NMM). PMM uses a mathematical cover system to describe the motion and deformation of a particle‐based physical domain. By introducing the concept of particle into NMM, PMM takes the advantages of easy topological and contact operations with particles. In this article, the methodology, formulations and implementation of the method are presented, together with modelling examples for validation. It is found that good solutions for both continuous and discontinuous problems are obtained by the new developed PMM. Due to the underlying coupled continuum‐discontinuum property of PMM, it has great potential for modelling of geomechanical problems. Copyright © 2012 John Wiley & Sons, Ltd.     

DATA RELATING TO THE STUDY OF THE PROBLEM OF GLACIATION IN THE LOWER YANGTZE VALLEY

In a commemorable evening—I believe it was in the early part of December, 1933—when I happened to discuss the problem of Pleistocene climate in China with the late Dr. Davidson Black, I informed him, without