3S技术支持下的小型遗址提取方法   总被引：1，自引：1，他引：0  

高飞  王心源  吴立  白恩亮  何磊 《地理空间信息》2009,7(4):75-78

针对仅利用地物光谱分析方法不能识别某些小型遗址的现状,提出基于地物空间关系知识,多源信息复合提取遗址的思路获取目标信息。以安徽省巢湖柘皋地区为例,利用SPOT-5卫星影像和地形图数据,综合运用3S技术进行小型遗址信息提取研究。经过和巢湖文管部门普查记录对比,证明了该方法有效性。该方法可缩小遗址探查范围,为考古普查工作节约大量时间、人力和物力。  相似文献   

Relational Agriculture: Gender,Sexuality, and Sustainability in U.S. Farming     

Isaac Sohn Leslie  Jaclyn Wypler  Michael Mayerfeld Bell 《社会与自然资源》2019,32(8):853-874

Although 97% of U.S. farms are “family-owned,” little research examines how gender and sexual relationships – inherent in familial dynamics – influence farmers’ practices and livelihoods. Gender and sexual dynamics – shaped by race and class – affect who is considered a farmer, land management decisions, and access to resources like land, subsidies, and knowledge. We use feminist and queer lenses to illuminate how today’s agricultural gender and sexual relations are not “natural,” but when left uninterrogated are constructed in ways that harm women and queer farmers while limiting potential to develop sustainable practices. Women and queer farmers also resist, “re-orienting” gender and sexual relations in ways that expand possibilities for achieving food justice and ecological sustainability. We offer “relational agriculture” as a tool for making visible and re-orienting gender and sexual relations on farms. Relational agriculture brings sexuality into food justice and demonstrates the centrality of gender and sexuality to agricultural sustainability.  相似文献   

山区农村土地利用转型与小农经济变迁耦合机理   总被引：1，自引：0，他引：1  

苏康传  杨庆媛  张佰林  张忠训 《地理研究》2019,38(2):399-413

通过山区土地利用转型与小农经济变迁的耦合关系分析,可以揭示山区人地关系的变化过程和机理。随着工业化、城镇化的快速推进,山区农村人地关系发生深刻变化,小农经济变迁驱动土地利用转型,土地利用转型进一步促进小农经济变迁。在阐述土地利用转型及小农经济变迁内涵和特征基础上,结合实证探讨二者间的耦合机理,以期为乡村振兴战略的实施提供理论支撑和现实参考。研究表明：① 山区农村土地利用转型与小农经济变迁相互影响,耦合演进。② 山区农村土地利用转型重点体现在农村宅基地、耕地及林地三类用地上。③ 中国小农经济已发生四次变迁,而山区小农经济变迁在第四次中表现较为明显,其阶段特征主要为农村人口向城镇迁移,土地流转频繁,土地规模经营趋势增强。④ 山区小农经济变迁引发耕地空间形态及功能转型,山区耕地转型进一步促进小农经济变迁。⑤ 山区小农经济变迁及农户生计策略非农化转变促使农户对宅基地结构及功能的需求发生变化;闲置废弃宅基地综合整治可显化农村土地资产价值,增加农民土地财产性收入,促进小农经济变迁。⑥ 通过云南省砚山县耕地利用转型案例剖析,验证了本文提出的山区农村土地利用转型与小农经济变迁的耦合机理。  相似文献   

Experimental investigation on a cabin-suspended catamaran in terms of motion reduction and wave energy harvesting by means of a semi-active motion control system     

《Applied Ocean Research》2019

A novel concept catamaran equipped with a suspended cabin, named Wave Harmonizer Type 4 (WHzer-4), is proposed and evaluated. The mass-spring-mass system is constructed by mounting four sets of suspensions in-between the cabin and the twin-hull. Two sets of dual motor/generators (M/Gs) are attached on the center beam of the cabin's deck fore and aft. Each shaft-end of the dual M/Gs is connected to the twin-hull through a rack-pinion gear unit. In this way the vertical relative motion between the cabin and the twin-hull can be transferred into the rotational motion of the M/Gs, and vice versa. A semi-active motion control system, which contains a proportional-integral (PI) controller, is designed and applied to each of the dual M/Gs for the aim of absorbing wave energy under the condition of suppressing the local vertical velocity of the cabin as much as possible. A 1/5 scale model ship with a length of 1.6 m is built, and a forced-oscillation bench test is implemented to validate the performance of the control system. Then, a series of towing tank tests is carried out in regular head waves. The heave and pitch responses of the cabin, those of the twin-hull and the corresponding wave energy capture width ratio (CWR) at five control scenarios and two reference scenarios are investigated. Discussion on the results of the tank test shows that the motion reduction of the cabin and the wave energy harvesting can be achieved simultaneously at a few wave conditions. However, at other conditions, although noticeable amount of wave energy is harvested, motion reduction of the heave and pitch of the cabin could not be obtained at the same time. It is suggested that varying the gain settings of the PI controllers according to the location of the controllers may improve the effectiveness of the proposed control system.  相似文献   

Effect of connecting rain barrels on the storage size reduction     

Yongwon Seo  Nam‐Jeong Choi  Daeryong Park 《水文研究》2012,26(23):3538-3551

In this article, the possibility of sharing rain barrels and the potential benefit of reducing storage size through physical and non‐physical connections of rain barrels in a community are investigated. Using the concepts of homogeneous/heterogeneous users in rainwater harvesting systems (RWHS), two simple cases of a community composed of four prospective users are examined. The first is performed with the users who have the same mean and variance in water demands (homogeneous users), and the second is with the users with different means and variances (heterogeneous users). To take account for the rainfall characteristics in different places, historical records from six cities in the USA are used for storage–reliability–yield analysis. The result indicates that required total storage can be reduced by connecting multiple rain barrels. In addition, a significant difference is found between homogeneous and heterogeneous user groups. Homogeneous users do not achieve a substantial benefit from connecting their rain barrels; these users may even be disadvantaged by sharing. In contrast, heterogeneous users receive benefit by reducing the total required storage. Most benefit is expected between users with maximum difference in mean water demands. The reduction in storage size was as considerable as 37% in this study. The quantity of storage reduction depends on locations and target reliabilities. Knowledge of the benefits and limitations of rain barrel connections can improve RWHS performance through ability to customize a network plan for individual users. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Effects of commercial timber harvesting on streamflow regimes in the Plynlimon catchments,mid‐Wales     

M. Robinson  A. Dupeyrat 《水文研究》2005,19(6):1213-1226

This paper presents the first large‐scale British study of the impacts of commercial forest cutting on stream‐flow regimes. The 70% forested headwaters of the River Severn are part of the intensively instrumented long‐term Plynlimon catchment study into the impact of land use on stream flow. The forest area, comprising predominantly Sitka spruce (Picea sitchensis), was planted mainly in the 1930s and 1940s. Harvesting commenced in the mid‐1980s and over the study period about half the forest has been felled. Changes in annual water yield and extreme flows were studied in four nested catchments ranging in area from about 1 to 10 km² and compared with an adjacent benchmark grassland catchment. As expected from earlier process studies the cutting of the forest increased total annual flows. Less expected was the clear evidence that the felling augmented low flows. This informs a long‐standing debate whether upland forestry increases or reduces baseflows. A particularly notable result was the lack of impact of the harvesting on storm peak flows. This may result from the application of forest management guidelines designed to reduce soil damage and erosion during the harvesting, and indicates that the forest itself has a limited impact on flooding. These findings are timely because British forest expansion peaked in the 30 years following the Second World War, and large areas of these woodlands are now approaching economic maturity and will be harvested in the next two decades. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A combined pyrolysis mass spectrometric and light microscopic study of peatified Calluna wood isolated from raised bog peat deposits     

Edwin van der Heijden  Jaap J. Boon 《Organic Geochemistry》1994,22(6)

Stem wood of the Angiosperm Calluna vulgaris (Scotch heather), isolated at different depths from a selection of raised bog peat deposits, was chemically characterized using in-source pyrolysis mass spectrometry (Py-MS) and Curie-point pyrolysis gas chromatography mass spectrometry (Py-GC-MS). Light microscopy was performed to relate mass spectrometric characteristics with anatomical features. Peatified wood samples, isolated from increasing depth show a gradual decrease in carbohydrate content. This decrease in anatomically reflected in a selective removal of secondary cell wall material from the fibre-tracheids and wood parenchyma. During prolonged peatification a selective removal of hemicellulose sugars is observed, while a part of the cellulose fraction is preserved. This highly resistant cellulose is mainly located in the secondary cell walls of the vessels. The lignin macromolecule is preserved, but a gradual decrease in syringyl to guaiacyl ratio (S/G) is observed during peatification. Because no increase in catechol and phenolic compounds is observed, we conclude that S/G shifts are due to removal the of syringyl-rich secondary cell wall material and the retention of guaiacyl-rich compound middle lamella. Small chemical changes in the lignin macromolecule involve shifts in oxygen substitutions on the aliphatic side chains of the methoxyphenolics and the occurrence of aromatic acids.  相似文献   

VENTILATION FLOW IN A BAROCLINIC VORTEX RELATED TO TROPICAL CYCLONE MOTION^*          下载免费PDF全文

Tian Yongxiang 《Acta Meteorologica Sinica》1995,9(3):338-348

The tropical cyclone motion is numerically simulated with a quasi-geostrophic baroclinic model.The flow field of a tropical cyclone is decomposed into its axisymmetric and asymmetric components.The relation between the ventilation flow vector and the motion vector of the tropical cyclone is investigated.The results of numerical experiments indicate:(1) There are both large-scale beta gyres and small-scale gyres in the asyrnmetric flow field.(2) The interaction between small-scale gyres and large-scale beta gyres leads to the oscillation of translation speed and translation direction for the tropical cyclone.(3) There are the large deviations between the ventilation flow vector calculated by means of Fiorino and Elsberry's method and the motion vector of tropical cyclone.(4) The ventilation flow vector computed using the improved method closely correlates with the motion vector of the tropical cyclone.  相似文献   

The role and value of local knowledge in Jamaican agriculture: adaptation and change in small-scale farming     

CLINTON BECKFORD  DAVID BARKER† 《The Geographical journal》2007,173(2):118-128

Local knowledge has played an active role in the lives of rural communities in virtually every part of the world. In Jamaica, traditional cropping systems based on local informal knowledge have been practiced since the days of slavery and play a vital role in meeting food security. Yet, some negative attitudes remain about the legitimacy and relevance of small-scale farmers' local and traditional knowledge. This paper discusses some conceptual and empirical issues related to the application of local knowledge among small-scale food farmers in central Jamaica. The paper argues that contextually speaking, local and traditional knowledge is valuable, adaptable and necessary in coping with risk and uncertainty in a changing world, while cautioning against a misguided notion of traditional knowledge as a panacea to all the ills of local agriculture.  相似文献   

人工集水面临界产流降雨量确定实验研究   总被引：8，自引：0，他引：8       下载免费PDF全文

李小雁  龚家栋  高前兆 《水科学进展》2001,12(4):516-523

通过在中国科学院寒区旱区环境与工程研究所皋兰生态农业试验站1998-1999年的降雨-径流观测实验,利用直线回归模型确定包括自然集水面在内的9种人工集水面的临界产流降雨量值(降雨阀值)。结果表明:在不受前期降雨影响下,自然黄土坡面、清除杂草自然黄土坡面和粘土夯实集水面的临界产流降雨量分别为8.5mm,8.0mm和4.1mm。在受前期降雨影响下,其临界产流降雨量分别为6.0mm,5.0mm和1.9mm。塑料膜、油毡、沥青和混凝土处理集水面的产流过程受降雨量和降雨强度的影响小,平均状态下其临界产流降雨量为0.1～1.5mm。塑料膜、油毡、沥青、塑料+小砾石和塑料+大砾石集水面的临界产流降雨量分别为0.13mm,0.21mm,0.17mm,0.98mm和0.85mm。混凝土集水面在干燥情况下的临界产流降雨量为1.48mm,在不干燥情况下的临界产流降雨量为1.16mm。  相似文献