Power intermittency, redundancy and tidal phasing around the United Kingdom     

JACK HARDISTY 《The Geographical journal》2008,174(1):76-84

The tidal resource is large in north-western European waters and a number of axial flow, vertical rotor and oscillating hydroplane schemes are approaching full-scale design and construction. However, the intermittency of the output from such devices that only generate electricity during the flood and ebb suggests that back-up generating capacity would be required with the associated inbuilt redundancy. Basic, shallow water tidal theory is reviewed and it is shown that carefully sized tidal stream installations in the Clyde, Tees, Humber, Severn, Menai Straits and the Mersey can utilise the phase locked occurrence of tidal flow and provide a more or less regular and continuous supply of electrical power to the National Grid. Estimates are given for the required capacity of the installations and a scheme is proposed by which an installed capacity of little more than, for example, 200 MW can provide a continuous supply of about 45 MW from these sites, thus achieving a significant and uninterrupted contribution to the Government's 2010 and 2020 targets.  相似文献   

Synchronization of late-glacial vegetation changes at Crystal Lake, Illinois, USA with the North Atlantic Event Stratigraphy     

Leila M. Gonzales  Eric C. Grimm 《Quaternary Research》2009,72(2):234-245

Late-glacial (17–11 cal ka BP) pollen records from midwestern North America show similar vegetation trends; however, poor dating resolution, wide-interval pollen counts, and variable sedimentation rates have prevented the direct correlation with the North Atlantic Event Stratigraphy as represented in the Greenland ice-core records, thus preventing the understanding of the teleconnections and mechanisms of late-Quaternary events in the Northern Hemisphere. The widespread occurrence of late-glacial vegetation and climates with no modern analogs also hinders late-glacial climate reconstructions. A high-resolution pollen record with a well-controlled age model from Crystal Lake in northeastern Illinois reveals vegetation and climate conditions during the late-glacial and early Holocene intervals. Late-glacial Crystal Lake pollen assemblages, dominated by Picea mariana and Fraxinus nigra with lesser amounts of Abies and Larix, suggest relatively wet climate despite fluctuations between colder and warmer temperatures. Vegetation changes at Crystal Lake are coeval with millennial-scale trends in the NGRIP ice-core record, but major shifts in vegetation at Crystal Lake lag the NGRIP record by 300–400 yr. This lag may be due to the proximity of the Laurentide ice sheet, the ice sheet's inherent slowness in response to rapid climate changes, and its effect on frontal boundary conditions and lake-effect temperatures.  相似文献   

欧美景观地理学的新进展及其启示   总被引：4，自引：0，他引：4  

汤茂林 《地域研究与开发》2005,24(4):12-16

文章从文化景观、景观概念、景观解释、景观与文化、景观政治学等方面阐述了欧美景观地理学的新进展。目前,欧美文化地理学正在重新整合,文化景观研究是其核心。针对景观的不同用法(艺术上的,社会科学上的),提出了4种专业化的景观解释模型。景观政治学是新文化地理学的关键建设领域,甚至有人把它当作景观解释的中心。地理学者对文学的兴趣日益增加,并将不同的文学形式看作是研究景观意义的途径。  相似文献   

砂土的物态本构模型     

邵生俊  谢定义 《岩土力学》2002,23(6):667-972

基于砂土的压缩回胀性、剪切非线性及剪缩剪胀性的系统分析和包括循环荷载、主应力轴旋转及应力路径偏转等复杂应力条件下的复杂变形反应,得到了三类应力-应变基本关系。在剪缩剪胀应力-应变关系中,引入了由偏应变分量确定的应变路径长度变量,揭示了应力主轴旋转、应力路径偏转引起的剪缩剪胀性。将这些基本关系与循环荷载下砂土的物态变化相联系,建立了砂土的物态动本构关系。  相似文献   

Foreword     

George W. Housner 《地震工程与工程振动(英文版)》2008,7(1):I0002-I0002

Destructive earthquakes have caused great damage in China and the United States and collapsing buildings have caused many deaths and injuries. The field of earthquake engineering studies earthquake hazards, the occurrence of earthquakes of various magnitudes, the nature of the ground shaking during an earthquake, the vibration of structures during earthquakes, the strengthening of existing structures and the design of new structures to be earthquake resistant, and finally, how to cope with earthquake damage and restore a city to normal functioning.  相似文献   

新版美国地震区划图源及其参数模型的分析与评述   总被引：6，自引：4，他引：2  

潘华  高孟潭  李金臣 《震灾防御技术》2009,4(2):131-140

2008年版《美国地震危险性图》（本文称“美国地震区划图”）采用5种类型震源区模型。本文全面分析了这些震源模型的划分目的、划分原则、基本特征、用途、各类型源间的相互关系,及其地震活动性参数确定的原则与基本方法。评述了美国地震区划图震源区模型及其地震活动性参数确定的特点和存在的问题。以期为我国新一代地震动参数区划图编制提供参考。  相似文献   

区域金融空间集聚与金融城市体系研究——基于美国外资银行的分析   总被引：1，自引：0，他引：1  

郑伯红 《世界地理研究》2009,18(2):29-37

周期性金融危机表明．大国的区域金融系统越来越融于全球资本流通和金融服务网络体系中,外资银行对东道国区域金融网络的空间组织发挥了重要作用,在促进区域金融流动的同时放大区域金融风险。本文总结了区域金融空间集聚与扩散的理论基础,以外资银行为例,论述了美国金融城市体系的规模和等级结构,分析了美国中心城市金融集聚特征与网络化趋势。  相似文献   

GrADS在数值产品分析中的开发应用   总被引：3，自引：0，他引：3  

黄毅梅  张超 《气象与环境科学》2000,(1):33-35

介绍了ＧｒＡＤＳ图形分析系统的编程方法,应用ＧｒＡＤＳ软件对数值模式的输出结果进行了编程处理,并结合实例介绍了它在实际中的多种程序设计和图形分析方法。  相似文献   

Comparison and analysis of agricultural and forest land changes in typical agricultural regions of northern mid-latitudes   总被引：1，自引：1，他引：0  

LIU Tingxiang  ZHANG Shuwen  TANG Junmei  LI Tianqi 《中国地理科学(英文版)》2013,23(2):163-172

The northeastern China, the United States, and the western Europe are important agricultural regions both on the global and regional scales. The western Europe has a longer history of agricultural land development than the eastern United States. These two regions have changed from the deforestation and reclamation phase in the past to the current land abandonment and reforestation phase. Compared with the two regions, large-scale land exploitation has only been practiced in the northeastern China during the last century. After a short high-intensity deforestation and reclamation period, agricultural and forest lands are basically in a dynamic steady state. By comparing domestic and international agro-forestry development and considering the ecological environment and socio-economic benefits that can be derived from agro-forestry, this paper suggests that large area of reforestation would be inevitable in future though persistent and large agricultural demand in coming decades even more. And local reforestation at slope farmland with ecological vulnerability should be imperative at present to avoid severer damage. At the same time, from the perspective of Land Change Science, the results demonstrate that the research on land use change in the agro-forestry ecotone is typical and critical, particularly those dealing with the analysis of spatial and temporal characteristics and the simulation of climate, hydrology, and other environmental effects.  相似文献   

Reliability-based load and resistance factor design approach for external seismic stability of reinforced soil walls     

《Soil Dynamics and Earthquake Engineering》2014

Load and resistance factor design (LRFD) approach for the design of reinforced soil walls is presented to produce designs with consistent and uniform levels of risk for the whole range of design applications. The evaluation of load and resistance factors for the reinforced soil walls based on reliability theory is presented. A first order reliability method (FORM) is used to determine appropriate ranges for the values of the load and resistance factors. Using pseudo-static limit equilibrium method, analysis is conducted to evaluate the external stability of reinforced soil walls subjected to earthquake loading. The potential failure mechanisms considered in the analysis are sliding failure, eccentricity failure of resultant force (or overturning failure) and bearing capacity failure. The proposed procedure includes the variability associated with reinforced backfill, retained backfill, foundation soil, horizontal seismic acceleration and surcharge load acting on the wall. Partial factors needed to maintain the stability against three modes of failure by targeting component reliability index of 3.0 are obtained for various values of coefficients of variation (COV) of friction angle of backfill and foundation soil, distributed dead load surcharge, cohesion of the foundation soil and horizontal seismic acceleration. A comparative study between LRFD and allowable stress design (ASD) is also presented with a design example.  相似文献