Anastomosis and the continuum of channel pattern

Anastomosing rivers are characterized by multiple channels separated by islands excised from the floodplain. Their status relative to the continuum concept of channel pattern is assessed with channel pattern defined in terms of three variables—flow strength, bank erodibility and relative sediment supply. Using an ordinal scaling (L(ow)–M(oderate)–H(igh)), the traditional forms of straight, meandering and braided have respective representations of (L,L,L), (M,L/M,L/M) and (H,H,M/H) in terms of those variables. The anastomosing pattern is on average represented by (L,L,M/H) but not so definitively as other forms. Specification of the third element (sediment supply) is particularly hampered by the paucity of data but aggradation, a characteristic of many anastomosing rivers, can be thought of as symptomatic of a moderately high rate of supply relative to the ability for onward transport. A sufficiently high rate of supply to a channel with low flow strength and resistant banks would induce shoaling and/or lateral constriction that locally forces flow out of the main channel and ultimately leads to the cutting of anabranches. A flow regime characterized by concentrated floods of relatively large magnitude is also regarded as highly conducive to the formation of new channels where low bank erodibility constrains channel capacity. Anastomosis may in certain cases represent a transitional form of channel pattern but there is no denying the longevity of some anastomosing systems.     

关于新时代实物地质资料科普发展的思考 ——以自然资源实物地质资料中心为例

实物地质资料是地质工作形成的最直接、最重要成果的体现,是地下地质情况最真实的信息记录载体,蕴藏着丰富的地质信息和地学知识,并具有原始性、唯一性、不可再生性、潜在价值巨大、获取成本高等特点,对我国国民经济建设和社会发展以及地球科学研究、地学科普等具有重要支撑作用。充分利用数字化、信息提取与挖掘、虚拟现实、互联网等技术,将实物地质资料科学、高效利用起来,切实转变实物地质资料科普观念,加强实物地质资料科普化研究,丰富实物地质资料科普形式,注重实物地质资料科普人才队伍建设,推进新时代实物地质资料科普工作高质量发展,进一步增强科普功能,提升新时代全民地球科学素养,对构建世界一流的岩芯管理体系具有重要现实意义。     

滇西北旅游业地域发展类型划分研究

运用旅游地生命周期理论划分区域旅游业地域发展类型是一个新的尝试。文章以滇西北旅游区大理、丽江、迪庆、怒江 4个旅游片区为旅游业发展地域单元。运用旅游地生命周期理论 ,结合各地域所处的发展阶段 ,以各地域的发展特征和定量指标为依据 ,定性分析与定量研究相结合 ,将滇西北旅游业发展划分为起步型、成长型和成熟型 3个地域类型 ,为进一步的普遍适用的旅游业地域系统发展类型划分提供实证研究依据。     

土地石漠化概念与分级问题再探讨

针对前人研究中将石漠化发生的地域限定在亚热带,将发生的时间限定在人类历史时期,将发生的原因均归结为人为不合理的经济活动,而忽视了石漠化可能发生的其它地域、其它时期和其它成因等问题,对土地石漠化概念作了修正。认为土地石漠化是在湿润、半湿润气候环境和岩溶环境中,由于人类活动和/或气候变化等因素作用,造成地表植被退化、土壤侵蚀、地表水流失、基岩裸露,形成类似石质荒漠景观的土地退化过程,并对其内涵作出释义。在此基础上依据生态基准面的理论,以坡面形态、溶蚀岩溶地貌形态、基岩出露率、土壤厚度和土被覆盖度、土壤侵蚀程度、植被覆盖率和植物种群、土地利用类型等为景观指征,将石漠化土地分为轻度、中度、重度和极重度4个等级,并以粤北岩溶山区为例,拟定了区域性石漠化土地分级及其综合景观指征。      

Teachers’ Concepts of Map-Skill Development

Maps are an increasingly used source of information and it is therefore essential to develop map skills in students. A fundamental factor affecting the choice of map skills and the way they are developed is the teacher and his/her concept of map work. Based on the results of a survey and semi-structured interviews among Czech teachers, this study identifies three basic conceptual types of teachers: “Navigators” and “Problem-Oriented” and “Source-Oriented” teachers. Similarities with teachers’ concepts of map-skill development identified in previous studies are discussed together with means of improvement.     

Application of the equilibrium planform concept to natural beaches in Northern Ireland

The equilibrium planform concept (EPC) for bayed beaches has achieved wide currency in coastal morphodynamics. The north coast of Ireland comprises a series of discrete headland-embayment beaches within which waves and currents recycle a finite sediment volume. It is therefore an ideal setting in which to explore the applicability of the concept. Application of the approach to 9 embayment beaches on the north coast of Ireland provides some insights into the application of the concept. The planform of some beaches does correspond to that predicted while others do not. Those whose measured planform does not correspond to the predicted planform can be interpreted through, (a) difficulty in identifying the wave diffraction point, (b) disequilibrium on the beach (sediment scarcity or excess), (c) geological control of beach morphology. The subjectivity in selecting the diffraction point renders alternative explanations difficult and reduces the utility of the approach on natural shorelines, where significant irregularities render identification of such points difficult.     

考虑各向异性的软黏土扰动状态本构模型

以大量试验结果为依据,运用物理意义明确、获取简便快捷、经济实用的土电阻率结构指标进行软黏土扰动变量的表征和测定。以三轴试验与电阻率测试结果为基础,进行了扰动函数的构建。在软黏土扰动状态描述中,引入旋转硬化因子,用以考虑应力诱发各向异性,进而构建了考虑各向异性的软黏土扰动状态概念本构模型。模型从一定程度上克服了传统扰动变量获取方法的弊端,克服了传统借用数学演绎手段建立扰动函数的不足,提高了模型应用的适用性。在模型构建中,融入初始应力各向异性的影响,从而使模型能更好地反映软土实际工程情况。三轴排水剪切试验验证结果表明,该模型可较好反映软黏土受荷下的结构变化情况和受力特性。     

城市化发展水平对生态环境压力的影响研究——以西安市为例

运用综合评价法对西安市1991—2007年的城市化水平进行了测度。同时,使用生态环境压力指数法对西安市城市生态环境压力进行了定量评价,并对城市化水平的各相关因子与生态环境压力指数之间进行了相关分析和回归分析。通过分析得出结论:城市化发展水平与生态环境压力之间存在着较明显的相关关系,其中城市现代化水平的发展是产生城市生态环境压力的主要原因,并提出了协调加快城市化进程与缓解城市生态环境压力之间矛盾的几点建议。     

基于扰动状态理论的软土压缩变形试验

基于扰动状态理论对漳州和东莞软土扰动样和重塑样单向压缩变形的结构性特征进行了分析,利用重塑样试验数据还原了原状样的压缩曲线,将变形中的土体视为相对完整状态和完全调整状态的混合物,定义原状土样为相对完整状态、重塑土样为完全调整状态,且分别用土弹性模型和修正剑桥模型表达,扰动函数与荷载对数具有较好的幂函数关系,因此建立了土体应力应变关系扰动状态模型,并通过压缩试验结果对模型合理性进行了验证。结果表明,该模型能较好地描述土体压缩变形特性,且参数确定简单易行,为软土地基工程沉降分析提供了一定参考。     

珠江三角洲大气边界层概念模型的建立及其应用

根据珠江三角洲地理环境、气候背景和边界层气象观测特征的分析,建立了反映珠江三角洲大气边界层一般机理的珠江三角洲大气边界层概念模型,可解释珠江三角洲地区环境空气质量变化的原因。本概念模型有助于开展珠江三角洲地区大气扩散能力的分析与气流停滞区或灰霾天气的预测预报。