河型转化机理及其数值模拟——Ⅰ.模型建立

为研究河型转化过程机理,建立了考虑弯道二次流影响与边岸崩塌过程的平面二维河流数学模型,包括水流模型、泥沙模型和边岸崩塌模型。通过在水流动量守恒方程中增加弥散应力项以考虑弯道二次流的影响,并采用室内水槽实验结果对水流模型进行了验证;利用上荆江沙市至石首天然长河段的水沙过程和河道演变资料,对泥沙模型进行了验证;结果表明本模型数值计算量合适,有较好的适应范围。模型中提出了边岸崩塌过程的模拟技术,相对于传统平面二维水沙模型而言,可以更好地模拟天然河道的横向摆动以及洲滩消长过程。     

隐伏岩体顶上带与深部成矿预测

岩浆侵入的流体流动模拟表明,侵入体上方是流体聚焦流动的位置,流体通量远大于旁侧围岩,流体在此产生沸腾作用。随温度降低,侵入体上方渗透率逐渐增大,最大渗透率出现在侵入体的顶部。含水岩浆侵位后在其顶上带发生二次沸腾和减压过程,释放出的巨大机械能远大于围岩的抗张强度,足以引起围岩发生脆性破坏。岩浆岩顶上带的水饱和外壳及其围岩发生破裂形成陡倾裂隙和水力破裂。直立长椭球状岩浆体的侵入会在岩浆岩顶上带产生放射状和同心圆状裂隙,同时产生爆破角砾岩筒。因此侵入体顶上带的岩钟、岩枝、岩脉,放射状、同心圆状裂隙和角砾岩筒均为构造弱化带,是热液矿脉密集发育的部位。矿床地质学研究已充分证明,岩浆岩顶上带确是容纳与中酸性岩浆有关的热液矿床的最佳部位。在开展深部成矿预测和找矿的过程中,探寻隐伏岩体顶上带和/或岩钟,是寻找深部与花岗岩类有关的多金属矿床的捷径。     

Experimental analysis of cross‐sectional flow motion in a large amplitude meandering bend

Flow in meandering bends is characterized by the formation of a large cross‐sectional central‐region circulation cell. The width‐to‐depth ratio is one of the most important parameters affecting the entity of the cross‐circulation motion. In steep outside bends, beside the central‐region cell, a counter‐rotating circulation cell often forms in the upper part of the outer‐bank. In spite of its practical importance, the evolving mechanisms of both the circulation cells and their role on boundary shear stress distribution in bends are not yet fully understood. The aim of the present paper is to gain some insight into how cross‐sectional flow motion evolves along meandering bends. Experiments have been carried out in a laboratory meandering channel of large amplitude, over a deformed‐rigid bed, for two values of the width‐to‐depth ratio. The three‐dimensional flow velocity field has been measured in detail at five cross‐sections, almost equally spaced along the channel reach between two consecutive apex sections. The measurements have been carried out on a fine grid by an acoustic Doppler velocity profiler. The distributions of the cross‐sectional flow (e.g. cross‐sectional flow velocity, net transversal flux) and turbulent kinetic energy are analyzed in each investigated section. Measurements show that the counter‐rotating circulation cell is evident only in the case of ‘small’ width‐to‐depth ratio. Such circulation cell begins at the bend entrance and it is fully developed at the bend apex; then it decays. At the bend apex, the core of maximum velocity is found near the bed at about the separation between the central and the outer‐bank circulation cells. Moreover, the presence of the counter‐rotating circulation cell allows the bank shear stress to maintain low values in the outer‐side of the bend. Copyright © 2010 John Wiley & Sons, Ltd.     

Curricular Changes in the Teaching of Geography in Swiss Upper Secondary Schools: An Attempt to Develop Skills for Lifelong Learning

Abstract

This article is an overview of the curriculum reform in Switzerland in the 1990s. It describes the grass-roots reform process in geography education in upper secondary schools and its impact on the development of new teaching materials. These ancillary materials are based on teaching methods and strategies, the effectiveness of which are empirically shown by results. The teaching units complement the thematic and methodological aims in the national curriculum and the federal regulations and were designed through a partnership of teachers, teacher educators and scientists. They can be translated directly into the practice of teaching and are available free to teachers through the World Wide Web.     

Changing Perspectives in High School World Geography: 1950–2005

Abstract

This study set out to better understand the changing links between geography and citizenship. Content analysis was conducted on eighteen high school world geography textbooks and state/national standards. Interviews were conducted with teachers and textbook authors. Five significant changes were noted: decline of national orientation and a greater focus on non-Western cultures; greater emphasis upon consumption over production; the accentuation of values clarification; increasing coverage of basic or prevocational skills; and standardization of format and content in textbooks. Many of these changes point towards a new cosmopolitan citizenship model, although some teachers and state social studies standards still see geography from a national perspective.     

Observational Work for Children

Abstract

Geographic information systems (GIS) are computer-based tools for geographic data analysis and spatial visualization. They have become one of the information and communications technologies for education at all levels. This article reviews the current status of GIS in schools, analyzes the requirements of a GIS-based learning environment from constructivist perspectives, and discusses the major issues in the design of a constructivist GIS-based learning environment based on experience from the development of World Explorer, a GIS-based learning environment that provides a theme-oriented data and information base, supports multiple representations and multiple linkages of information, and facilitates interactive learning and knowledge construction.     

Implementation and Effectiveness of GIS-Based Projects in Secondary Schools

This study aims to provide an understanding of the main obstacles to conducting GIS-based projects in secondary schools and to determine the effects of these projects on students, teachers, and schools. The study was conducted in three public high schools in Turkey. The students first surveyed over 4,015 people in their school districts to understand the main social, environ- mental, and economic problems in their area, then conducted nine different GIS-based projects to help design solutions to these problems. As seen in the study, GIS is a very important teaching and learning tool for secondary schools; however, its effective use depends on planning, motivation, support, resources, time, and enthusiasm, especially for teachers.     

Bulletin Boards in Geography

Abstract

Teaching geography within a field-based, environmental-problem-solving framework integrates geographic knowledge and practice and introduces high school students to skills required to undertake geographic research. A five-day field investigation on coastal geography was designed for juniors at a science high school in New Jersey. The goal of the field investigation was to allow students to engage in problem-solving, gather field data, apply geographic concepts and tools, and foster the ability to think critically. The purpose of the investigation was to identify the spatial distribution of litter on a beach and interpret the distribution based on physical and human processes. The field site is a 400-m-long shoreline reach in Raritan Bay, New Jersey. Students defined the term “litter” for purposes of the investigation, developed a classification system, and mapped the location and type of litter on the beach. Three sampling grids were established across the beach from the dune crest to the waterline. Students conducted topographic surveys of the sampling grids, collected litter in each grid cell, and counted, classified, and weighed the litter. Data gathered were reduced, analyzed, and interpreted based on the published literature. Findings were presented at a formal presentation on the last day of the investigation. Students submitted a written report and presented the results of the investigation at a student conference two months later. Field investigations can expose students to different methods of data sampling and measurement. Collaboration between secondary schools and universities can result in successful learning initiatives that allow students the opportunity to experience the role of a practicing professional.     

咸宁核电厂首批次级测量控制网的建立及分析

介绍了咸宁核电厂次级网设计的原则及实施过程中的注意事项,分析了采用GPS静态定位方式下的数据观测、数据处理控制方法,对GPS基线边长质量控制采用高精度全站仪进行了边长观测比较分析。     

矿区地表移动变形监测数据处理

本文采用AutoCAD VBA二次开发技术,实现了地表移动观测数据处理、成图自动一体化.克服了传统方法成图只能查看、不易定量分析的缺点;在输出下沉、倾斜、曲率、水平移动、水平变形计算结果的同时,将各移动变形曲线和对应的地下煤层开采情况按一定比例尺在CAD中成图.可实现从图中曲线上直接量取任意点的对应值;较方便地从图中求...