利用照片建模技术重建文物的三维数据模型

基于照片的三维建模技术是指直接通过二维数码照片来重建物体的三维数据模型。根据照片建模的基本方法和基本原理,利用该建模技术实际完成了重庆大学校内一尊塑像的三维数据模型的建立。照片建模技术在文物遭遇自然灾害或者意外事件之后的成功应用表明,文物的三维模型重建和文物保护等方面具有一定的实用价值和推广应用前景。     

馆藏文物保护中数字建模技术应用研究

随着三维扫描技术的发展,三维扫描技术的应用范围逐步扩大。在文物保护领域,三维扫描技术也有着重要的应用。同时,作为博物馆数字化的一个重要组成部分,馆藏文物保护与修复的数字化技术也在不断深入。因此,首都博物馆文物保护分析实验室应用三维激光扫描技术开展了一系列在文物保护分析过程中的数字建模工作,特别是对文物修复和复制的辅助作用进行了有益的尝试。针对工作过程中遇到的技术难点诸如偏色、背景干扰等进行了分析,并提出解决办法,旨在供文物保护领域和计算机技术领域共同探讨研究。     

Factors affecting fluid flow in strike–slip fault systems: coupled deformation and fluid flow modelling with application to the western Mount Isa Inlier, Australia

Deformation and focused fluid flow within a mineralized system are critical in the genesis of hydrothermal ore deposits. Dilation and integrated fluid flux due to coupled deformation and fluid flow in simple strike–slip fault geometries were examined using finite difference analysis in three dimensions. A series of generic fault bend and fault jog geometries consistent with those seen in the western Mount Isa Inlier were modelled in order to understand how fault geometry parameters influence the dilation and integrated fluid flux. Fault dip, fault width, bend/jog angle, and length were varied, and a cross-cutting fault and contrasting rock types were included. The results demonstrate that low fault dips, the presence of contrasts in rock type, and wide faults produce highest dilation and integrated fluid flux values. Increasing fault bend lengths and angles increases dilation and integrated fluid flux, but increasing fault jog length or angle has the opposite effect. There is minimal difference between the outputs from the releasing and restraining fault bend and jog geometries. Model characteristics producing greater fluid flows and/or gradients can be used in a predictive capacity in order to focus exploration on regions with more favorable fault geometries, provided that the mineralized rocks had Mohr–Coulomb rheologies similar to the ones used in the models.     

贾湖骨笛复原新技术研究

贾湖骨笛是迄今为止我国历史上最早、形态完整、现今仍可演奏的吹管乐器,是9000～7500年前中国古代科技文明最重要的实物载体之一。由于骨笛经历数千年的埋藏,出土时多数已经破损。如何对破损的贾湖骨笛进行精确复制,是学界急待解决的难题。我们巧妙地利用CT扫描、数据处理、三维模型重建、虚拟复原与激光快速成型技术,复原出与M494:2号骨笛实物十分接近复原品。这种利用计算机虚拟修复的思想与技术为破损贾湖骨笛的复原开辟了一条新的技术途径。     

New occurrence of Cambroclavus absonus from the lowermost Cambrian of North China and its stratigraphical importance

Li, L.-Y., Zhang, X.-L., Yun, H. & Li, G.-X., October 2015. New occurrence of Cambroclavus absonus from the lowermost Cambrian of North China and its stratigraphical importance. Alcheringa 40, xxx–xxx. ISSN 0311-5518.

The problematic Small Shelly Fossil Cambroclavus absonus is described from the Xinji Formation in the Longxian area, which is located near the southwestern margin of the North China Platform. The Xinji Formation, the basal rock unit of the Cambrian in the studied area, yields an assemblage of skeletal fossils that share many common elements with contemporary faunas from South Australia. Sclerites of C. absonus reported herein represent the first occurrence of the species outside Australia, thus extending the palaeogeographic range of the taxon to northern China. To date, palaeogeographic occurrences of Cambroclavus sclerites are restricted to the Peri-Gondwana realm, including South China, Australia, Tarim, Kazakhstan, North China and Western Europe. These occurrences are divided into a Southern Group realm and Northern Group realm. Stratigraphically, Cambroclavus occurs mostly in Cambrian Stage 3 and has three occurrences in Stage 5, separated by Stage 4 in which Cambroclavus has not yet been found. The first appearance datum of Cambroclavus in Cambrian Stage 3 is of importance for regional and inter-regional correlations. In particular, the presence of Cambroclavus absonus in North China allows species-level correlation between North China and South Australia.

Luoyang Li [lly@stumail.nwu.edu.cn], Xingliang Zhang [xzhang69@nwu.edu.cn], Hao Yun [yunhao@stumail.nwu.edu.cn], Early Life Institute and State Key Laboratory Of Continental Dynamics, Department of Geology, Northwest University, Xian 710069, PR China; Guoxiang Li [gxli@nigpas.ac.cn], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China.     

Discrete Element Analysis of the Minimum Thickness of Oval Masonry Domes

This study focuses on domes the ground plan of which, instead of the more common circular shape, is an oval, and aims at finding the minimally necessary uniform wall thickness for domes of different geometries loaded by their selfweight. The discrete element code 3DEC was applied because of its capability of simulating the collapse mechanisms of masonry structures. Results on the minimal wall thickness, corresponding masonry volume and failure mechanisms for different dome geometries are presented. Three ranges of the friction coefficient were found. For very low frictional resistance collapse happens with pure frictional sliding, for any arbitrarily large wall thickness. In the range of relatively high (i.e., realistic) friction coefficients the structure collapses without any sliding if the wall is not sufficiently thick, and in the observed range of the friction coefficient the necessary wall thickness is nearly insensitive to its value (collapse initiates with hinging cracks only). Between the two domains an intermediate behavior was found: combined cracking and sliding collapse modes occur for insufficient wall thickness, and the minimal thickness strongly depends on the friction coefficient. The critical and transitional friction coefficients separating the failure modes were determined for different eccentricities of the groundplan.