THE MOST PERFECT EXAMPLE OF AN ALIEN ECOLOGY EVER CONSTRUCTED     

《The Professional geographer》2013,65(4):471-477

Much science-fiction literature is based upon the creation and exploration of alternative environments. Stanley G. Weinbaum's short story, “Parasite Planet,”introduces an unusual environment that may be wrong in the light of recent evidence on Venus but still stimulates the geographical imagination.  相似文献   

MÉTHODE D'ÉTUDE DES NAPPES LIBRES DANS LES AQUIFÈRES ANISOTROPES     

Claude VIGUIER 《水文科学杂志》2013,58(1):21-27

Abstract

The necessary and sufficient conditions for non-zero phase shift and non-zero attenuation in linear flood routing can be derived from the continuity equation alone and are found to depend on the existence of an imaginary part in the expression for frequency or in the expression for wave number. It is shown that in linear flood routing the phase lag between flow rate and area of flow is directly related to the attenuation per unit wave length. The effects of using various forms of the momentum equation, in addition to the continuity equation, are exemplified by deriving analytical expressions in terms of the frequency, both for attenuation per unit channel length and for phase shift, for the kinematic wave, the general diffusion analogy, and the complete St. Venant equation.  相似文献   

台站电源远程管理单元的实现          下载免费PDF全文

王小明  陈婧  张勇 《地震工程学报》2013,35(S1):158-161

由电源测控单元、短信平台及远程控管平台构成的上海市地震局台站电源远程管理单元,实现了对台站市电、UPS、电池组等设备状态的实时监控,对台站电池组的远程充放电功能,以及对台站电源故障的短信告警,为用户提供了可视化的台站电源状态报表,提高了用户对电源故障的处理效率和台站设备运行率。  相似文献   

岷县漳县M_s6.6地震前平凉台地电场变化          下载免费PDF全文

范莹莹  安张辉  陈军营  刘君  王建军  崔腾发  王丽 《地震工程学报》2013,35(4):827-834

应用2013年甘肃岷县漳县M_s6.6地震前263天及震后9天的平凉台观测数据研究了该台地电场在时间域、频率域内的变化,得到:(1)在岷县漳县M_s6.6地震以及在2013年四川芦山M_s7.0地震前平凉台地电场观测记录了显著的自然电场变化,在近距离的岷县漳县地震前自然电场变化更显著,异常变化的持续时间长;(2)平凉台地电场最大熵功率谱密度在4月20日四川芦山地震前发生连续增大的现象,并持续到甘肃岷县漳县地震后。最后讨论了本次地震地电场极低频成分异常变化的机理。  相似文献   

Improvement of streams hydro‐geomorphological assessment using LiDAR DEMs     

Pascale M. Biron  Guénolé Choné  Thomas Buffin‐Bélanger  Sylvio Demers  Taylor Olsen 《地球表面变化过程与地形》2013,38(15):1808-1821

Hydro‐geomorphological assessments are an essential component for riverine management plans. They usually require costly and time‐consuming field surveys to characterize the spatial variability of key variables such as flow depth, width, discharge, water surface slope, grain size and unit stream power throughout the river corridor. The objective of this research is to develop automated tools for hydro‐geomorphological assessments using high‐resolution LiDAR digital elevation models (DEMs). More specifically, this paper aims at developing geographic information system (GIS) tools to extract channel slope, width and discharge from 1 m‐resolution LiDAR DEMs to estimate the spatial distribution of unit stream power in two contrasted watersheds in Quebec: a small agricultural stream (Des Fèves River) and a large gravel‐bed river (Matane River). For slope, the centreline extracted from the raw LiDAR DEM was resampled at a coarser resolution using the minimum elevation value. The channel width extraction algorithm progressively increased the centerline from the raw DEM until thresholds of elevation differences and slopes were reached. Based on the comparison with over 4000 differential global positioning system (GPS) measurements of the water surface collected in a 50 km reach of the Matane River, the longitudinal profile and slope estimates extracted from the raw and resampled LiDAR DEMs were in very good agreement with the field measurements (correlation coefficients ranging from 0 · 83 to 0 · 87) and can thus be used to compute stream power. The extracted width also corresponded very well to the channel as seen from ortho‐photos, although the presence of bars in the Matane River increased the level of error in width estimates. The estimated maximum unit stream power spatial patterns corresponded well with field evidence of bank erosion, indicating that LiDAR DEMs can be used with confidence for initial hydro‐geomorphological assessments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

前兆定点形变观测数据噪声分析   总被引：1，自引：0，他引：1  

刘俊清  丁广  张晨侠  王雨萌 《地震地磁观测与研究》2013,(5):182-187

地球物理研究表明,可以构造或选择合适的统计模型模拟观测噪声,从而了解噪声特性,获得噪声谱及其含量.对吉林省5个台站的倾斜观测共18个测项产出的时间序列进行噪声分析,结果表明,长期观测噪声可用带通噪声和随机游走噪声的组合模型模拟,短时间观测噪声可用谱指数介于-1至-2的幂律噪声模型模拟.该结论对定点形变观测噪声的认识、噪声源的研究以及地壳构造信息的提取具有参考意义.  相似文献   

Beach morphodynamic characteristics and classifications on the straight coastal sectors in the west Guangdong     

Ding  Yuanting  Yu  Jitao  Cheng  Huangxin 《地理学报(英文版)》2020,30(7):1179-1194

Journal of Geographical Sciences - Currently beach morphodynamic classification is the most important foundation to conduct associated coastal geomorphological studies. This paper carried out beach...  相似文献   

Evaluation of the half‐power bandwidth method to estimate damping in systems without real modes     

Bertha A. Olmos  Jose M. Roesset 《地震工程与结构动力学》2010,39(14):1671-1686

The objective of this work was to assess the significance of the values of damping obtained applying the half‐power bandwidth method to the frequency response records of the steady‐state response of a system that does not possess real modes either because the damping matrix does not satisfy the orthogonality condition or because its parameters are functions of frequency. A multi‐degree of freedom system with real modes and different types of damping is considered first. A two degree of freedom system with an arbitrary damping matrix, a rigid mass on an elastic foundation subjected to vertical and coupled horizontal/rocking vibrations, and a single degree of freedom model of a building accounting for inertial soil structure interaction effects are considered next in more detail. The results show that the predictions of the method, when applicable compare very well with those provided by approximate formulae and procedures used in practice. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

风沙活动强度的常用判断指标及其应用评述   总被引：5，自引：3，他引：2  

李晋昌  苏志珠  胡光印 《中国沙漠》2010,30(4):788-795

风沙活动是风力作用下地表物质被吹蚀、搬运和再沉积的过程, 其强度主要决定于风力和下垫面状况两个因素。对风沙活动强度的判断在防沙和治沙研究中长期应用,近年来也成为全球变化研究中经常涉及到的指标之一,尤其是对气候变化和干旱化、沙漠化等研究。列举了国内外常见的18种风沙活动强度的判断指标,对各自的原理、应用方法和适用条件进行了详细的描述和分析,并认为沙漠化面积和湖泊沉积记录可能并不适合作为判断指标,并且各指标之间缺乏可比性,重新建立一种可适用于不同时空尺度的判断指标应是今后研究的重点,这将对反映风沙活动的演变历史、预测未来的发展趋势及指示中国黄土高原的形成环境均有极为重要的意义。  相似文献   

区域创新集群发展的关键要素及作用机制研究——以日本创新集群为例   总被引：1，自引：0，他引：1  

倪外  曾刚  滕堂伟 《地域研究与开发》2010,29(2)

在分析创新集群的构成与创新机制的基础上,从外部环境、构成主体等4个方面讨论了创新集群与产业集群的区别。以日本创新集群发展为例,分析创新集群的关键创新要素及作用机制,研究发现:在知识经济和经济区域化发展背景下,区域创新集群已成为促进区域产业升级与提升竞争力的核心力量;在创新集群发展中,领先企业的创新主导与示范作用突出,但又通过技术权力以技术锁定、标准控制等各种不同方式实施技术控制,影响中小型企业及其他研发机构发挥创新作用;在技术传播中,技术扩散、技术转移、技术溢出同时存在,在不同主体、不同阶段、不同空间尺度之间的途径与作用效果不同,畅通的技术通道保证了创新的共创共享;社会网络以社会文化、制度基础保障了各成员主体间经济学意义上最经济的创新合作与交流;创新平台构建了多要素、多功能、多层次的创新系统,体现了创新集群的整体创新优势。此外,行业协会也是创新集群形成与发展的重要基础。  相似文献