Predicting reach‐specific properties of fluvial terraces to guide future fieldwork. A case study for the Late Quaternary River Allier (France) with the FLUVER2 model

Numerical models have not yet systematically been used to predict properties of fluvial terrace records in order to guide fieldwork and sampling. This paper explores the potential of the longitudinal profile model FLUVER2 to predict testable field properties of the relatively well‐studied, Late Quaternary Allier system in France. For the Allier terraces an overlapping ¹⁴C and U‐series chronology as well as a record of ¹⁰Be erosion rates exist. The FLUVER2 modelling exercise is focused on the last 50 ka of the upper Allier reach because for this location and period the constraints of the available dating techniques are tightest. A systematic calibration based on terrace occurrence and thicknesses was done using three internal parameters related to (1) the sediment erodibility; (2) the sediment transport distance; and (3) the sediment supply derived from the surrounding landscape. As external model inputs, the best available, reconstructed, tectonic, climatic and base‐level data were used. Calibrated model outputs demonstrate a plausible match with the existing fluvial record. Validation of model output was done by comparing the modelled and measured timing of aggradation and incision phases for the three locations. The modelled range of landscape erosion rates showed a reasonably good match with existing erosion rate estimates derived from ¹⁰Be measurements of fluvial sands. The quasi‐validated model simulation was subsequently used to make new testable predictions about the timing and location of aggradation and erosion phases for three locations along the Allier river. The validated simulations predict that along the Allier, reach‐specific dynamics of incision and aggradation, related to the variations in sediment supply by major tributaries, cause relevant differences in the local fluvial terrace stratigraphy. Copyright © 2016 John Wiley & Sons, Ltd.     

Digital Archiving and On-line Publishing of Old Relief Models

Abstract

Although people rarely think of relief models when speaking about cartographic products, these artefacts are probably the most impressive way of visualizing landscapes. Unlike traditional maps or globes, most relief models are unique, vulnerable hand-made objects. Digital archiving is an important step in their preservation. There are special tools for this task, but these equipments are rather expensive, and libraries or other institutes that usually own these models cannot spend too much. The authors examined various on-line tools to create digital 3D representation of relief models using a set of photographs as source. These tools create point cloud and textured triangle mesh based on matching patterns on the photos. A workflow was developed which uses these web services and produces the digital 3D version of relief models. This paper introduces the method, discusses the details of successful photographing, the possible post-processing of the results. A new web site, using the X3DOM technology to show the digitized models to the general public, is also introduced.     

视频对象分割及跟踪方法研究

讨论和分析了视频对象全自动提取及后续帧中的跟踪过程及采用的方法,对其算法、分割性能和结果进行了比较和评述。并结合Hausdorff和Snake跟踪器,对初始对象轮廓进行跟踪。结果证明,这种跟踪方法能有效地解决对象被遮挡和形变以及背景移动的问题。     

一个湍能封闭模型对风暴潮海底底应力的应用研究

将一个三维湍能封闭模型应用于开阔海区的风暴潮，通过数值计算探讨了Ｔａｙｌｏｒ底摩擦二次率的拖曳系数随空间的分布及拖曳系数与水深、海底粗糙度、风向和风速等因素的关系。本文对底摩擦二次率的可靠性做了评价。     

红板岩材料隐式本构模型的建立及其应用研究

针对红板岩材料在岩土工程中所表现的大量模糊的和不确定的因素等特点,基于人工神经网络的学习能力,借助于室内岩石力学试验,进行了对该材料的力学本构特性进行了神经网络模拟研究,提出了隐式本构模型的思想和方法,并通过该方法对该岩石的流变试验结果进行学习,获得了以网络权值结构保存的力学特性知识,由此得到了表征红板岩应力应变本构关系的隐式本构模型。应用结果表明,该方法对岩土类材料本构关系的模拟研究具有很好的应用前景。     

象山皇城海滩稳定性分析与防护对策

以浙江岬湾砂质海岸象山皇城海滩为例,运用抛物线模型,分析得出皇城海滩的冲淤演化动态,并通过历史岸线形态对比探讨皇城海塘对其的影响,最终提出防止海岸侵蚀的对策。研究结果表明,皇城海滩北部有一定的侵蚀,其平面形态还未达到静态平衡,处于不稳定状态;皇城海滩北段海塘修建得过于靠海,致使海滩最重要的泥沙补给源——后滨沙丘被阻断,甚至消失,同时大潮水位可直接淹没海塘堤脚,加上海塘前为近破波,滩面水流和泥沙运动剧烈,最终导致堤前滩面的冲刷。基于此,防止海岸侵蚀的最佳对策是在拆除、重建海滩北部部分海塘后再进行适当的海滩养护。通过对皇城海滩的稳定性研究,了解海塘建设的影响,可为浙江岬湾海滩资源的合理开发、海岸防护工程建设提供一定的科学依据。     

湘鄂赣二叠纪岩相古地理研究

湘鄂赣二叠纪沉积盆地是在华南陆块基础上发育而成,具有扬子克拉通北缘被动大陆边缘盆地、扬子克拉通盆地、湘赣板内拉张盆地和华夏克拉通边缘盆地等四类。根据古暴露等标志,建立了各类盆地的沉积层序,并进行了区域对比。在此基础上,本文着重运用层序地层编图法编制了湘鄂赣二叠纪岩相古地理图,深化了该区岩相古地理研究,详细建立了沉积体系域模式和岩相古地理演化特点和控制因素。     

THE APPLICATION OF IMAGE-BASED MODELING IN PALEOEARTHQUAKE TRENCH STUDY

The geological structure exposed by paleoearthquake trenches is the key material to the right cognition of fault activity and paleoearthquake. However, paleoearthquake trenching inevitably destroys active tectonic geomorphic evidence and trench exposures are usually difficult to reserve. The conventional process of recording the delicate geological information, manually constructing photomosaics by image-editing software, is time-consuming and produces undesirable artificial distortions. Herein, we explored the process of constructing trench orthophotomosaics and the 3D image model using the Image-based Modeling technology and applied it to the Liutiaohe trench across the Tianqiaogou-Huangyangchuan Fault, Gansu Province. Based on the 3D image modeling and orthophotomosaic, we firstly constructed the control points and scale bars on cleaned trench walls and collected photos of all sections of the trench with a digital camera in the field, and then reconstructed the 3D model of the trench through the Agisoft PhotoScan, an efficient image-based modeling software, and finally yielded the 3D image model of the trench and othophotomasaics of the trench exposures. The results show that the automated workflow can produce seamless, sub-millimeter-level high-resolution photomosaics more quickly, with precision in the centimeter range, and the 3D image model is of great help to identify strata and geological structures in trenches with much lower capital and labor costs and low expertise levels compared with LiDAR, meanwhile, the 3D archive benefits the share and communication and even allows future reinterpreting the site using new insights.     

流速逆变张量隐式求解方法及其在航道港池流场计算中的应用

运用高分辨率的边界适应网格进行流体动力学数值计算时,如何提高计算稳定性和减少计算量成为数值求解的关键性问题.在非正交的边界适应坐标系中,每个动量方程中同时出现了两个交叉方向的水位偏导数项,给隐式求解带来困难,而显式格式下的时间步长由于受与空间步长有关的Courant-Friedrichs-Lewy条件限制,计算量成倍增加.本文从广义曲线坐标系下浅海动力学方程组出发,导出了流速的逆变张量所满足的动量方程组,使方程中的水位偏导数项变成了沿某一协变基向量方向占优的形式,方便地采用了交替方向隐式差分格式,从而提高了计算稳定性并减小了计算量.本文通过对澳门海域航道和港池中流场的计算,证实了该模式是一种进行高分辩率数值计算的有效方法.     

Tropospheric Ozone in a Global-Scale Three-Dimensional Lagrangian Model and Its Response to NOX Emission Controls

A three-dimensional Lagrangian tropospheric chemistry modelis used toinvestigate the impact of human activities on the tropospheric distributionofozone and hydroxyl radicals. The model describes the behaviour of 50 speciesincluding methane, carbon monoxide, oxides of nitrogen, sulphur dioxide andnineorganic compounds emitted from human activities and a range of other sources.Thechemical mechanism involves about 100 chemical reactions of which 16 arephotochemical reactions whose diurnal dependence is treated in full. The modelutilises a five minute chemistry time step and a three hour advection timestepfor the 50,000 air parcels. Meteorological data for the winds, temperatures,clouds and so on are taken from the UK Meteorological Office global model for1994 onwards. The impacts of a 50% reduction in European NO_Xemissions onglobal ozone concentrations are assessed. Surface ozoneconcentrations decrease in summertime and rise in wintertime, but to differentextents.