Impacts of forest structure on precipitation interception and run‐off generation in a semiarid region in northern China          下载免费PDF全文

Jiakai Liu  Zhenming Zhang  Mingxiang Zhang 《水文研究》2018,32(15):2362-2376

Water resource scarcity and uneven distribution are 2 major environmental issues in China today. Forest structure is a dominant factor that influences hydrological processes, but the specific interactions remain uncertain due to the predominant use of individual or 1‐dimensional forest structure metrics in previous studies. In this study, forest structures in 8 run‐off plots on Mount Miaofeng in north China were parameterized by metrics of different dimensionalities. The relation between canopy interception and forest structure, shrub/litter interception, and forest structure as well as run‐off and forest structure were analysed by regression method and validated by leave‐one‐out cross test. The results showed that canopy interception rates ranged from less than 0.10 all the way to 0.80, affected by forest structure and precipitation, with interception rate decreasing logarithmically as precipitation increased. Forests with a larger canopy area (CA), leaf area index (LAI), and higher average height (H) had a narrow range of canopy interception rates, and forest with larger value of diameters at breath height (DBH), H, LAI, vertical heterogeneity coefficient (T), and structure complexity index (SCI) had higher interception rates. Forests with higher value of DBH, H, and horizontal heterogeneity coefficient (R) had higher shrub/litter interception rates on the forest floor. The run‐off coefficient was only significantly associated with LAI, T, and SCI. The validation test indicated that regression analysis of canopy interception rates and shrub interception are reliable and SCI is a key factor to influence the run‐off coefficient. However, the regression results of litter interception have a relatively large error. According to the results, to reduce the risks of the landslides and floods, forest managers should complicate the canopy and preserve trees with thicker stems and larger canopies. By contrast, to obtain more water resource from run‐off in arid regions, forest managers should harvest trees with large canopies and construct complex vertical structures by intermediate cutting.  相似文献   

定向钻井技术在阜康煤层气示范工程中的应用          下载免费PDF全文

汤建江  黄建明  刘蒙蒙 《探矿工程》2018,45(1):28-30

新疆阜康白杨河矿区煤层气开发利用先导性示范工程是新疆第一个煤层气开发利用示范工程。新疆阜康白杨河矿区地形复杂,多为山地丘陵,地层具有“高倾角、多煤层、大厚度”的地质特点,示范工程部署的井型大部分为丛式井,因此定向钻井技术得到广泛应用。本文主要从示范工程现有井排采情况,分析了井身质量对管杆偏磨的影响,并从钻具组合和定向工艺优化等几个方面对本地区定向钻井技术进行了研究,同时对该技术在本区块应用过程中出现的一些问题进行了探讨,为今后该区块定向钻井技术的推广应用奠定了技术基础。  相似文献   

垂直不均匀分层的地基GPS层析水汽研究     

陈宏斌  熊永良  陈志胜  徐晓莉  葛玉辉 《测绘工程》2015,(5)

依据四川省内GPS数据研究垂直分层方法对层析结果的影响及大气水汽随着高程变化的特点,提出一种垂直不均匀分层方法。与垂直均匀分层进行对比实验,不均匀分层的层析结果与探空水汽结果更吻合。由于水汽主要集中在对流层中低层,对流层低层的垂直分辨率相对较高,采用垂直不均匀分层方法得到的大气水汽的变化特征更加细致。考虑到水汽分布的不均匀特点,认为垂直不均匀分层更符合大气水汽的实际分布。四川地区的水汽层析实验研究结果表明文中提出的垂直不均匀分层方法可行且有效。  相似文献   

Editorial – transformation of cities     

Lars Winther 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2015,115(2):67-72

Cities and city regions are on the global agenda as key sites for contemporary societal development, in terms of agglomeration of economic activity, places of everyday life and dense networks. The majority of economic, political and social activities is today formed by urbanisation, and an increasing number of people are living and working in city regions. At the same time, many cities and peripheral regions are struggling with job losses, industrial restructuring and depopulation, and thus, many countries face new forms of spatially economic and social inequalities. This special issue is about the contemporary urbanisation processes and the transformation of cities and urban systems in the European context using Denmark as a particular case. Denmark provides a present-day example of urban transformation, and its urban system resembles that of many other European countries – Denmark having one large urban centre and a long tail of smaller cities and towns. Thus, the papers in this issue provide insights into contemporary urban changes.  相似文献   

新型仿生PDC齿高效切削机理及试验研究     

刘婧  高科  徐小健  李梦 《探矿工程》2013,40(12):5-8

利用仿生耦合理论,根据贝壳和蝼蛄等动植物的非光滑形态结构研制了一种新型的仿生PDC齿,并利用有限元软件abaqus对单个齿磨损前后的运动过程进行分析,与普通PDC齿的应力分布状态进行对比,可以看出,在同等条件下,非光滑PDC切削齿的应力大小及分布情况要明显优于普通的PDC切削齿,具有良好的碎岩效果。此外还对这2种切削齿进行了磨耗比试验,试验结果进一步证明了仿生PDC齿具有一定的优越性。  相似文献   

A COMPUTER SOLUTION FOR DETERMINING STUDENT MIGRATION∗     

《The Professional geographer》2013,65(3):249-254

Western investment and trade in East-Central Europe is likely to play a key role in the economic fortunes of the region over the next decade. Currently, the capital cities and the western parts of Poland, Czechoslovakia, and Hungary are the primary beneficiaries of economic interaction with the West. As such, existing regional inequalities are being reinforced. Deepening regional socioeconomic disparities within individual states could complicate the economic restructuring process and jeopardize state stability in the years ahead.  相似文献   

Influence of Bedding Dip on Glacial Erosional Landforms,Uinta Mountains,USA     

Marissa H. Kelly  Alison M. Anders  Sara Gran Mitchell 《Geografiska Annaler: Series A, Physical Geography》2014,96(2):147-159

We explore the relationships amongst bedding dip, basin aspect, and glacial landforms using field observations and GIS analyses of the northwestern Uinta Mountains of Utah. We examine basins on opposing sides of three ice divides in which quartzite beds of the Mount Watson Formation maintain a near constant dip. These areas provide contrasting relationships between ice flow and bedding dip directions while holding rock type and climate constant. We map the occurrence of three glacial erosional landforms: cliffs showing evidence of quarrying, scoured surfaces polished by abrasion, and overdeepenings. Cliffs and overdeepenings are more common in basins where bedding dips up‐basin, while scoured surfaces are more prevalent where bedding dips down‐basin. The significance of jointing in controlling glacial erosional forms is well established and we propose that bedding, as well as joints, dictates the geometry of quarried blocks and influences the spatial patterns of process dominance. Where bedding dips up‐basin, the geometry of pre‐existing weaknesses favours quarrying creating both cliffs and overdeepenings. In contrast, where bedding dips down‐basin, block geometry does not favour the creation of overdeepenings via quarrying and exposed bedding planes are subjected to glacial abrasion, producing scoured surfaces.  相似文献   

THE UNEVEN DEVELOPMENT AND SPATIAL DIFFUSION OF CHINESE CENTRAL CITIES     

宁越敏  严重敏 《中国地理科学(英文版)》1994,4(2):119-128

ＴＨＥ ＵＮＥＶＥＮ ＤＥＶＥＬＯＰＭＥＮＴ ＡＮＤ ＳＰＡＴＩＡＬ ＤＩＦＦＵＳＩＯＮ ＯＦ ＣＨＩＮＥＳＥ ＣＥＮＴＲＡＬ ＣＩＴＩＥＳ ＮｉｎｇＹｕｅＡｎｎ（宁越敏）；ＹａｎＺｈｏｎｇｍｉｎ（严重敏）（ＴｈｅＩｎｓｔｉｔｕｔｅｏｆＧｅｏｇｒａｐ...  相似文献   

Exploiting West Africa's children: trafficking, slavery and uneven development   总被引：1，自引：0，他引：1  

Kate Manzo 《Area》2005,37(4):393-401

This paper analyses child trafficking and slavery in relation to media coverage of West African children, international law and academic research within geography and development studies. The meaning and practice of child trafficking is examined in the context of related debates about child labour, exploitation and uneven development. The analysis highlights key differences between trafficking and slavery, thereby illuminating the varying forms of exploitation at work in different relations of power.  相似文献   

Laboratory simulation of clast abrasion     

J. Lewin  P. A. Brewer 《地球表面变化过程与地形》2002,27(2):145-164

Experimental abrasion of river‐bed materials has been widely undertaken, producing ‘downstream’ fining rates that generally are believed to be much less than those observed in the field. A conclusion commonly adopted has been that sorting processes are more effective than abrasion processes. A comparative evaluation of results from an abrasion tank and a tumbling barrel are presented, which show that abrasion patterns and rates differ according to the equipment used, clast size and shape, the clast charge (barrel) and water velocity and bed material (tank). Abrasion is a composite process, and the effects achieved appear to be dominated by percussion in the tank and grinding in the barrel. Breakage, crushing and sandblasting are not modelled effectively, nor are effects achieved on clasts when they form part of the bed. Comparisons are made with other equipment used, the very limited amount of direct field abrasion monitoring, and with the probable suite of processes that may occur under field conditions. Also reviewed are the problems that arise when laboratory weight‐loss abrasion coefficients are used or converted into ones of size diminution, as usually derived from field observations of down‐channel trends. It is concluded that field abrasion rates generally have been underestimated, as the processes involved are at best only selectively represented by the experimental equipment so far used, and because the results obtained experimentally are capable of misinterpretation when related to field trends. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献