山东省城市人口-城区面积的异速生长特征探讨   总被引：6，自引：0，他引：6  

刘继生  陈彦光 《地理科学》2005,25(2):135-141

基于不同的城市定义标准,对山东省城市体系的城市人口和城区面积进行分析,发现只有地级市明确地服从异速生长定律,而县级市的关系则不够明朗。研究表明,山东省城市人口-城区面积异速生长的标度因子均小于1,而且定义的城区越小则标度因子越大。由此可见,山东省城市体系的城区扩展速度整体上比较合理,不过在中小城市郊区地带的土地利用比大城市郊区地带要浪费一些。山东城市人口-城区面积异速生长关系的状态不是很好,这暗示城市体系的发展存在许多不协调的因素,借助数学模型变换揭示了其中结构退化的实质所在。文章指出,只有通过自组织方式在城市之间形成一种自下而上式竞争-合作关系,才能进一步完善城市体系的时空结构。  相似文献   

近30年来鄱阳湖生态系统服务变化   总被引：1，自引：0，他引：1  

陈旻坤  徐昔保 《湖泊科学》2021,33(1):309-318

鄱阳湖是我国最大淡水湖,在维持区域生态安全和生态平衡中发挥重要作用.为了解近30年鄱阳湖生态系统服务变化情况,本文对已有文献与监测数据进行收集整理,直接获取鄱阳湖水资源供给、渔业资源供给、水环境净化服务数据,通过输沙量法、Berger-Parker优势度指数计算泥沙淤积调控和生物多样性维持服务,利用RMSD方法分析19922014年鄱阳湖生态系统服务关系.结果表明:(1)渔业资源供给和水环境净化服务不断下降,水资源供给和泥沙淤积调控服务在2010s有所恢复;(2)冬候鸟种类和数量增加,鱼类种群结构逐渐恢复,但Berger-Parker指数总体上升;(3)浮游植物、底栖动物多样性上升,浮游动物多样性下降;(4)不同时间尺度各服务间均为高权衡关系,水环境净化服务相对收益始终高于其他服务.  相似文献   

What is the role of the model in socio-hydrology? Discussion of “Prediction in a socio-hydrological world”*   总被引：1，自引：1，他引：0  

Lieke Anna Melsen  Jeroen Vos  Rutgerd Boelens 《水文科学杂志》2018,63(9):1435-1443

Srinivasan et al. provide an interesting overview of the challenges for long-term socio-hydrological predictions. Although agreeing with most of the statements made, we argue for the need to take socio-hydrological analysis a step further and add some fundamental considerations, especially concerning the crucial importance of many (conscious and unconscious) assumptions made upfront of the modelling exercise. Eventual assumptions of technological determinism need correction: Models are not “value-free”, but uncertain, subjective and a product of the society in which they were shaped. It is important to acknowledge this uncertainty and bias when making decisions based on socio-hydrological models, considering also that these models are “social and political actors” in and by themselves. Furthermore, socio-hydrological models require a transdisciplinary approach, since physical water availability is only one of the boundary conditions for society. Last but not least, interaction with stakeholders remains important to enable understanding of what the variable of interest is.  相似文献   

Modelling Near-Surface Low Winds over Land under Stable Conditions: Sensitivity Tests,Flux-Gradient Relationships,and Stability Parameters   总被引：1，自引：1，他引：0  

Ashok K. Luhar  Peter J. Hurley  Ken N. Rayner 《Boundary-Layer Meteorology》2009,130(2):249-274

Low or weak wind-speed conditions, roughly defined as the periods when the mean wind speed at 10 m above the ground is 2 ms⁻¹ or less, are of considerable practical interest. However, they are not readily amenable to treatment within prognostic meteorological models and, consequently, difficult to predict, especially when the ambient stability is strong. In this paper, we apply an E − ε prognostic meteorological model to simulate near-surface meteorology and, focusing on low wind speeds, compare the predictions with measurements from two independent datasets. A sensitivity analysis is performed to investigate the possible reasons for the relatively inferior model performance for low winds when the atmosphere is stably stratified. A comprehensive data analysis is carried out to study low wind stable conditions, concentrating on the validity of various forms of flux–gradient relationships for momentum and heat within the framework of the Monin-Obukhov similarity theory, which models employ for calculating surface fluxes. The observed behaviour of various stability parameters, such as the Richardson number, is investigated. The results point to inadequacies of the current flux–gradient relationships, especially regarding momentum, under strongly stable conditions as being a dominant reason for the poor low wind predictions. The modelling issues identified are not just restricted to the present model, but are general in nature. The use of an alternative stability function for momentum under strongly stable conditions is explored. It results in improved model performance for low winds; however, further research is needed to better understand strongly stable flows in the lower atmosphere and to develop methods that can translate that understanding to operational meteorological modelling.  相似文献   

Property matters: Agricultural restructuring and changing landlord-tenant relationships in England     

Brian Ilbery  Damian Maye  Lewis Holloway 《Geoforum》2010,41(3):423-434

Little research has been conducted on the restructuring activities of tenant farmers in response to changing tenancy legislation and recent CAP reforms. This paper examines the geography of farm tenancy agreements in England since 1995 and presents some findings from postal and telephone surveys on the possible future business trajectories of tenant farmers and the changing nature of landlord-tenant relationships. A clear north-south divide is identified in terms of farm tenancy agreements and a complex array of different tenancy agreements is demonstrated. The relationships between landlords and tenants are changing and the increasing variety of agreements provides evidence of a more fluid (post-feudal) system of agricultural leases. Nevertheless, high levels of uncertainty and negativity characterise tenant farmers’ views on the impacts of CAP reforms. Crucially, the very identity of a tenant farmer is changing, towards an owner-occupier who rents additional land, and there is an urgent need for more detailed research on the ‘consequential geographies’ of farm property rights and the changing nature of landlord-tenant relationships.  相似文献   

体/体拓扑关系计算研究     

沈敬伟  温永宁  闾国年  吴明光 《测绘科学》2012,(4):120-122

GIS不仅关心空间目标自身的时间、空间和属性特征,还必须能够处理其与所处环境间的关系。体/体拓扑关系计算是三维空间目标之间拓扑关系计算的难点,为此,本文提出一种体/体拓扑关系计算方法:基于点集拓扑理论,利用维度扩展的9交模型(DE-9IM)对体/体之间存在着的8种有意义的拓扑关系进行描述;通过比较空间目标各部分(内部、边界和外部)的交集,从而判断空间目标之间的拓扑关系;设计了一个体/体拓扑关系计算算例,对算法进行详细阐述;最后,设计了体/体拓扑关系计算实验,验证了方法的有效。  相似文献   

Second homes and urban growth in the Oslo area,Norway     

《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3):154-165

Urban growth and second homes are claimed to be closely connected, partly because urban growth can ‘push’ second homes out from former rural areas, and partly because second homes may have a role to play in urban growth. The article discusses such a connection based on a study conducted in the Oslo area of Norway. The analysis shows that second homes and urban growth to some degree are connected in Oslo, but that governmental regulations hinder a potentially stronger connection. This is partly due to a ban on new second homes in some areas, and partly because regulations obstruct second home areas from being transformed into residential areas. Further, there has been a rise in the numbers of Oslo inhabitants owning second homes in new and growing second home areas located at increasingly greater distances from the city. Such areas are thus contributing to a diffusion of urban space in rural areas. Finally, the study highlights how urban growth is only one factor influencing the location of second homes owned by inhabitants of Oslo, while scarcity of available land and changes in demand are additional variables.  相似文献   

TRIZ:研究人地关系问题的一种新的理论与方法   总被引：1，自引：0，他引：1  

孙峰华  朱传耿  王振波  孙东琪 《地理研究》2012,31(10):1737-1748

我国地理学家认为应该加强人地关系问题的综合集成研究。目前我国人地关系问题研究, 在技术设计解决问题上尚属空白, 为此, 引入TRIZ.TRIZ解决问题的基本观点有技术系统、技术矛盾、创新等级、理想状态;解决系统中矛盾问题的理论基础是技术系统演变的8个法则。TRIZ解决问题的方法主要是使用分析工具和知识库, 分析工具主要包括矛盾矩阵、物-场模型与标准解法、ARIZ、需求功能分析;知识库主要包括40个创新原理、解决矛盾问题的原则、76个标准解、效应数据库。TRIZ解决问题的程序主要是识别问题、选择工具和方法、解决矛盾问题的方案评估。以武汉市青山区为案例, 探讨了TRIZ解决区域人地关系矛盾问题的思路、理论、方法和强大功能, 构建了TRIZ理论解决区域人地关系问题的逻辑范式。结论指出, TRIZ不仅适用于技术领域, 也适用于非技术领域, 将为今后人地关系问题研究提供一种新视野、新理论、新方法。  相似文献   

P-SV波和SS波反射系数之间的近似关系   总被引：3，自引：0，他引：3  

孙鹏远  孙建国  卢秀丽 《地球学报》2004,25(6):677-682

本文通过对Aki&Richards给出的P SV波反射系数的一阶近似 ,给出了一个新的描述P SV波和SS波反射系数之间关系的近似公式。在 4个不同类型的含油气砂岩模型上的定量计算表明 :新的近似关系能够反映SS波阻抗和P SV波反射系数之间的内在关系 ,而且形式简单、近似效果好、适用范围广 ,适合于SS波阻抗的定量反演和理论研究 ;如果再结合PP波AVO信息 ,还可以简单、准确地进行多参数反演。另外 ,在 2 0°以内 ,利用该近似关系 ,纯SS波零偏移距剖面和P SV转换波剖面之间可以相互转换。  相似文献   

Non-linear quickflow response as indicators of runoff generation mechanisms     

Charles I. Scaife  Nitin K. Singh  Ryan E. Emanuel  Chelcy Ford Miniat  Lawrence E. Band 《水文研究》2020,34(13):2949-2964

Linking quickflow response to subsurface state can improve our understanding of runoff processes that drive emergent catchment behaviour. We investigated the formation of non-linear quickflows in three forested headwater catchments and also explored unsaturated and saturated storage dynamics, and likely runoff generation mechanisms that contributed to threshold formation. Our analyses focused on two reference watersheds at the Coweeta Hydrologic Laboratory (CHL) in western North Carolina, USA, and one reference watershed at the Susquehanna Shale Hills Critical Zone Observatory (SHW) in Central Pennsylvania, USA, with available hourly soil moisture, groundwater, streamflow, and precipitation time series over several years. Our study objectives were to characterise (a) non-linear runoff response as a function of storm characteristics and antecedent conditions, (b) the critical levels of shallow unsaturated and saturated storage that lead to hourly flow response, and (c) runoff mechanisms contributing to rapidly increasing quickflow using measurements of soil moisture and groundwater. We found that maximum hourly rainfall did not significantly contribute to quickflow production in our sites, in contrast to prior studies, due to highly conductive forest soils. Soil moisture and groundwater dynamics measured in hydrologically representative areas of the hillslope showed that variable subsurface states could contribute to non-linear runoff behaviour. Quickflow generation in watersheds at CHL were dominated by both saturated and unsaturated pathways, but the relative contributions of each pathway varied between catchments. In contrast, quickflow was almost entirely related to groundwater fluctuations at SHW. We showed that co-located measurements of soil moisture and groundwater supplement threshold analyses providing stronger prediction and understanding of quickflow generation and indicate dominant runoff processes.  相似文献