基于核磁共振的不同含水率黄土古土壤冻融循环试验研究

为明确不同含水率古土壤在冻融循环作用下其微观结构特性及古土壤损伤机制,采用核磁共振扫描仪对不同含水率冻融循环后的古土壤试样进行测试,研究冻融循环和含水率共同作用对古土壤微观结构的影响及土体内部损伤变化。结果表明:冻融循环下不同含水率使土体内部产生不同程度的损伤,损伤程度为含水率大的土体大于含水率小的土体。随着冻融循环次数增加,T₂谱曲线信号幅度增加,孔隙结构改变,大孔隙、最大孔隙含量增加,中孔隙含量减小; 同时含水率较大的土体孔隙体积增大幅度大于含水率较小的土体,说明在季节冻土区建设工程中含水率越大土体越易发生破坏,因此在工程中应注意防排水问题。依据损伤力学原理,得出土体颗粒连续性与孔隙率关系,进而得出有效应力与孔隙率关系; 根据核磁扫描结果,建立孔隙率与冻融循环次数关系,最终推导出古土壤有效应力与冻融循环次数关系表达式。研究成果为季节冻土区古土壤地层建设工程提供理论指导。     

济阳坳陷前古近纪烃源岩生烃潜力分析

济阳坳陷前古近系发育多套低勘探程度层系,下古生界寒武系—奥陶系、上古生界石炭系—二叠系和中生界都具有一定的生烃能力并可以提供油气资源。不同地质时期构造和沉积背景的差异形成了具有不同地球化学特征的烃源岩。本文综合地质资料、烃源岩热解和TOC分析资料、镜质体反射率资料、全岩显微组分分析资料、饱和烃和芳香烃色质资料等,系统分析了济阳坳陷前古近系烃源岩分布特征、地化特征和资源潜力。下古生界海相碳酸盐岩系烃源岩分布局限,有机质丰度较低,但类型较好,具有一定的供烃能力。上古生界煤系烃源岩分布范围广,有机质丰度较高,有机质类型相对较差,以生气为主,复杂的构造演化特征导致了这套源岩以二次生气为主。中生界发育了煤系源岩和湖相泥岩两套烃源岩,有机质类型中等,局部发育中等—好烃源岩,成熟度空间差异较大。总体来看,济阳坳陷三套前古近系烃源岩中,上古生界煤系源岩品质最佳,中生界次之,下古生界相对较差。     

碳封存砂岩储层的孔隙迂曲度分形特征研究

目前“双碳”减排的背景下,砂岩咸水层是最具潜力的二氧化碳封存介质,其孔隙结构特征决定了流体的运移及封存效率,对其进行研究具有重要的科学意义。分形维数常用于定量表征砂岩孔隙结构在三维空间中的分布规律,但以往对砂岩孔隙迂曲度分形特征进行研究时,多依赖于孔隙率、平均孔隙半径、平均迂曲度等特征值计算分形维数,并不能很好的反映岩石孔隙排列分布及孔隙连接的非均质性。文章将砂岩孔隙结构概化为具有迂曲度的毛细管,首先通过核磁共振成像（MRI）技术获取岩石片层图像,以盒维数法获得孔径分布分形维数;随后以孔径分布分形维数为目标值,结合不同迂曲度下的毛细管数量与孔径的分形标量关系,迭代计算迂曲度分形维数。与传统的分形维数计算方法相比,该研究确定的迂曲度分形维数更能体现岩石内部不同孔隙排列方式引起的迂曲度差异。     

西南天山复杂地层绳索取心钻探跑钻事故处理方法

新疆西南天山萨尔干矿区地层极其破碎复杂,近年来施工的钻孔多全孔破碎、漏失,钻进过程中时有掉块、卡钻、钻孔坍塌等现象发生,严重时发生孔内事故,施工难度较大。本文结合该区一例钻孔施工案例,介绍了破碎复杂地层取心钢丝绳断裂导致岩心内管脱落,进而引发严重跑钻事故的处理过程以及注意事项。结合现场事故情况,通过导向扩孔钻进等方法有效地处理了该起复杂事故,使钻孔得以顺利终孔,取得了所需地质资料,挽回了经济损失。     

Viscosity and nonlinearity effects on the forces and waves generated by a floating twin hull under heave oscillation

Nonlinear hydrodynamics of a twin rectangular hull under heave oscillation is analyzed using numerical methods. Two-dimensional nonlinear time-domain solutions to both inviscid and viscous problems are obtained and the results are compared with linear, inviscid frequency-domain results obtained in [26] to quantify nonlinear and viscous effects. Finite-difference methods based on boundary-fitted coordinates are used for solving the governing equations in the time domain [2]. A primitive-variables based projection method [6] is used for the viscous analysis and a mixed Eulerian–Lagrangian formulation [11] for inviscid analysis. The algorithms are validated and the order of accuracy determined by comparing the results obtained from the present algorithm with the experimental results of Vugt [22] for a heaving rectangle in the free surface. The present study on the twin-hull hydrodynamics shows that at large and non-resonant regular frequencies, and small amplitude of body oscillation, the fluid viscosity does not significantly affect the wave motion and the radiation forces. At low frequencies however the viscosity effect is found to be significant even for small amplitude of body oscillation. In particular, the hydrodynamic force obtained from the nonlinear viscous analysis is found to be closer to the linear inviscid force than the nonlinear inviscid force to the linear inviscid force, the reason for which is attributed to the wave dampening effect of viscosity. Since the wave lengths generated at smaller frequencies of oscillation are longer and therefore the waves could have a more significant effect on the dynamic pressure on the bottom of the hulls which contribute to the heave force, the correlation between the heave force and the wave elevation is found to be larger at smaller frequencies. Because of nonlinearity, the wave radiation and wave damping force remained nonzero even at and around the resonant frequencies – with the resonant frequencies as determined in [26] using linear potential flow theory. As to be expected, the nonlinear effect on the wave force is found to be significant at all frequencies for large amplitude of oscillation compared to the hull draft. The effect of viscosity on the force, by flow separation, is also found to be significant for large amplitude of body oscillation.     

Equilibrium trading of climate and weather risk and numerical simulation in a Markovian framework

We consider financial markets with agents exposed to external sources of risk caused, for example, by short-term climate events such as the South Pacific sea surface temperature anomalies widely known by the name El Nino. Since such risks cannot be hedged through investments on the capital market alone, we face a typical example of an incomplete financial market. In order to make this risk tradable, we use a financial market model in which an additional insurance asset provides another possibility of investment besides the usual capital market. Given one of the many possible market prices of risk, each agent can maximize his individual exponential utility from his income obtained from trading in the capital market, the additional security, and his risk-exposure function. Under the equilibrium market-clearing condition for the insurance security the market price of risk is uniquely determined by a backward stochastic differential equation. We translate these stochastic equations via the Feynman–Kac formalism into semi-linear parabolic partial differential equations. Numerical schemes are available by which these semilinear pde can be simulated. We choose two simple qualitatively interesting models to describe sea surface temperature, and with an ENSO risk exposed fisher and farmer and a climate risk neutral bank three model agents with simple risk exposure functions. By simulating the expected appreciation price of risk trading, the optimal utility of the agents as a function of temperature, and their optimal investment into the risk trading security we obtain first insight into the dynamics of such a market in simple situations.

Transportation Part II

Abstract

This article presents research on evaluating problem-based learning using GIS technology in a Singapore secondary school. A quasi-experimental research design was carried to test the PBL pedagogy (PBL-GIS) with an experimental group of students and compare their learning outcomes with a control group who were exposed to PBL but not GIS. The results show significant differences in the learning outcomes between the two groups. Specifically, students in the control group show more memorization skill while students in the experimental group demonstrate more analytical and evaluation skills. The conclusion is that learning with PBL-GIS pedagogy can result in higher-order learning outcomes.     

The Global Landscape of GIS in Secondary Education

This study analyzes the status of GIS in schools in thirty-three countries and proposes recommendations for advancing the implementation and effectiveness of GIS in secondary education from an international perspective. Thirty-three countries have been evaluated in the study to assess the global landscape of educational GIS by analyzing how GIS is recognized, approached, and used across the world with chief challenges, opportunities, and case studies. As the study revealed, the current global landscape of GIS remains small for secondary education; however, the convergence of citizen science, emphasis on spatial thinking, mobile devices, open data, and Web-based map services could cause a significant increase in the numbers of schools, educators, and students teaching and learning with GIS.     

基于WebGIS的汶川地震次生地质灾害信息管理系统

汶川地震次生地质灾害数量多、分布广且类型复杂,严重威胁灾区人民的生命财产安全。为了分析次生地质灾害发育分布规律,并用于减灾防灾,急需一种有效的方法来对现场调查获取的大量地质灾害数据进行管理。以信息建模理论为指导,运用统一建模语言UML,并结合GIS空间数据模型分析,以建立面向对象的空间数据模型,及实现海量地灾信息综合管理为目的,研发了汶川地震次生地质灾害信息综合管理系统(WIMS)。利用GIS的强大空间图形管理能力、数据库技术以及网络开发等技术,以发布图形服务与数据服务的方式实现地质灾害数据共享,解决了空间数据编辑及提升地图访问速度的关键技术问题。该系统不仅能够为灾害管理部门制定防治方案提供一定的参考依据,并且能够为广大群众提供一个认识地质灾害的公共平台,提高全民防灾意识。     

基于GIS和视频监控的森林防火指挥决策系统研建

森林火灾能对森林资源造成巨大的危害,因此发现林区火源并进行科学决策具有重要意义.本系统数据主要包括1∶1万地形图、1∶1万森林资源二类调查数据、扑火队分布数据、瞭望台站数据、扑火物资储备数据、林业局管理机构分布数据、研究区2010年landsat TM遥感影像图等;系统功能主要包括数据的处理和管理、森林火灾监测、最佳扑火路径分析、防火扑火预案制定和决策、森林火险等级评价、林火趋势模拟和预测、灾害损失评估、相关图表和报告制作等.系统采用Microsoft Visual Studio 2005(C#)作为开发语言,基于Arc Engine 9.3组件进行二次开发,三维地图显示采用skyline Terra Explorer开发平台,数据库采用SQL Server 2005数据库管理系统,利用Arc SDE 9.3空间数据库引擎对空间数据进行管理.