A visco‐elasto‐plastic model for granular materials under simple shear conditions

The numerical simulation of rapid landslides is quite complex mainly because constitutive models capable of simulating the mechanical behaviour of granular materials in the pre‐collapse and post‐collapse regimes are still missing. The goal of this paper is to introduce a constitutive model capable of capturing the response of dry granular flows from quasi‐static to dynamic conditions, in particular when the material experiences a sort of solid‐to‐fluid phase transition. An ideal assembly of identical spheres under simple shear conditions is considered. In the constitutive model, void ratio and granular temperature have been chosen as state variables, and both shear and normal stresses are computed as the sum of two contributions: the quasi‐static one and the collisional one. The former is determined by using a perfect elasto‐plastic model including the critical state concept, while the latter is derived from the kinetic theory of granular gases. The evolution of the granular temperature, fundamentally governing the material phase transition, is obtained by imposing the kinetic fluctuating energy balance. The constitutive relationship has been integrated, under both constant pressure and constant volume conditions, and the influence of shear strain rate, initial void ratio and normal pressure on the mechanical response has been investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

高分辨率遥感影像自动生成DEM的研究

以三江源测区为研究对象,采用传统法和影像自动匹配法进行DEM制作。通过试验研究及对比分析发现:两种方法制作的DEM均能满足精度要求,传统法精度高,过程流畅,工艺纯熟,不足之处是工期较长;影像自动匹配法制作的DEM精度虽不及传统法高,但其工期短,工效是传统法的5倍左右。考虑到在满足精度要求的前提下,作为提高作业效率的一种方法,影像自动匹配法大规模制作DEM可应用于实际生产。     

The use cases of digital earth

Abstract

The formal process of system design begins with the identification of use cases. No such cases are readily apparent for the current generation of geobrowsers, though the text of the 1998 Gore speech refers to several. An analysis of the use cases of geographic information systems (GIS) reveals similarities with the functionality of geobrowsers, inviting the view that the two forms of geographic information technology will eventually converge. However, experience suggests that users are finding very different ways of exploiting geobrowsers, and two examples are discussed in detail. These uses can be interpreted within a broad framework of spatial concepts, and the paper concludes that this framework provides a better guide to the future of geobrowsers and Digital Earth than current GIS technology.     

内河数字航道的概念与构成研究

针对当前内河数字航道概念不清、构成不完整的问题,在新时期内河航道发展转型需求分析的基础上,系统地阐述了内河数字航道的基本概念,建立了由航道模型规范、航道条件监测、航道数据资源、航道养护管理、航道信息服务、航道运行保障等构成的内河数字航道体系,简述了对转型需求的支撑关系,对于加快和推进我国内河数字航道的标准化建设具有重要的意义。     

信息化质检系统数据库设计

针对国内大多测绘质检软件还仅限于满足成果质检需要的现状,该文提出了面向所有地理信息产品信息化质检系统的构建思想,采用数据库设计的理论和方法,详细论述了满足信息化质检系统的数据库概念模型结构及关系模型结构。基于该数据库模型,研发了测绘地理信息产品质量检验与评价系统。实践应用表明,该数据库模型能够满足信息化质检系统的需要。但数据库设计是一个不断优化的过程,在应用开发过程中可根据具体情况进一步完善。     

辅助模型辨识方法(5):最小二乘辨识

借助于辅助模型辨识思想,针对白噪声干扰的输入非线性有限脉冲响应系统,研究了辅助模型最小二乘辨识方法、辅助模型多新息最小二乘辨识方法、变递推间隔辅助模型最小二乘辨识方法、变递推间隔辅助模型多新息最小二乘辨识方法、等递推间隔辅助模型多新息最小二乘辨识方法,以及有限数据窗最小二乘辨识方法,包括引入加权因子（加权矩阵）、遗忘因子得到的一些相应辨识方法.     

城市新区与城市功能的关联耦合机制

基于城市新区与母城关系的复杂性特征,开展城市新区与母城功能之间关联理念、关联互动和关联要素的定性分析。从适配理念入手,在母城功能外溢和新区功能承接的基础上,针对居住型、产业型和综合型3种不同类型的新区,从居住、工业和生产性服务业3个业态类型进行关联耦合。坚持适配理念可以使城市新区功能的能性、能级和能位与城市整体功能相适应,有助于城市新区与母城功能之间关联耦合,保障城市健康发展。     

A thermo‐hydro‐mechanical model for unsaturated soils based on the effective stress concept

A simple thermo‐hydro‐mechanical (THM) constitutive model for unsaturated soils is described. The effective stress concept is extended to unsaturated soils with the introduction of a capillary stress. This capillary stress is based on a microstructural model and calculated from attraction forces due to water menisci. The effect of desaturation and the thermal softening phenomenon are modelled with a minimal number of material parameters and based on existing models. THM process is qualitatively and quantitatively modelled by using experimental data and previous work to show the application of the model, including a drying path under mechanical stress with transition between saturated and unsaturated states, a heating path under constant suction and a deviatoric path with imposed suction and temperature. The results show that the present model can simulate the THM behaviour in unsaturated soils in a satisfactory way. Copyright © 2010 John Wiley & Sons, Ltd.     

以科学发展观统领测绘工作初探

为贯彻落实科学发展观对测绘工作的要求,应以科学发展观统领国土资源测绘工作全局,充分利用测绘成果以及现代测绘技术,为推进科学发展提供保障服务。     

Concept Mapping Strategies: Content,Tools and Assessment for Human Geography

Abstract

This article examines the use of concept mapping for formative and summative assessment of northeast Florida middle school students’ knowledge of human geography. The students were participants in an afterschool, academic, college reach-out program that provided opportunities to test concept mapping strategies that support spatial thinking and stimulate interest in human geography. The study documents the use of concept mapping for assessment of seventh graders’ achievement of a specific lesson and for students’ human geography achievement across all implementation grades. Concept mapping results provided insight into aspects of the curriculum and instruction where appropriate modifications could better facilitate meaningful learning.