一种面向栅格的空间-属性双重约束聚类方法     

刘敬一  薛存金  樊彦国  孔凡萍  何亚文 《地球信息科学学报》2017,19(4):447-456

针对栅格数据,传统聚类方法大都基于专题属性进行聚类,分裂了栅格对象的空间特性与专题属性,而兼顾空间与专题属性的现有空间聚类方法又存在算法复杂、参数设置多等问题,因此本文提出了一种面向栅格的空间-属性双重约束聚类算法（A Raster-oriented Clustering Method with Space-Attribute Constraints, RoCMSAC）。RoCMSAC利用栅格数据空间邻域和空间连通特性,重新定义栅格簇的相似性度量准则,通过属性均质簇生成,空间相邻栅格簇合并和空间邻近栅格簇合并3个步骤对栅格数据进行空间-属性双重约束聚类。利用太平洋海域海表温度栅格数据对算法的可行性以及有效性进行验证,并与现有算法进行对比分析。通过实例验证与对比发现：① RoCMSAC方法能够保证栅格簇空间域的邻近性和属性域的均质性;② RoCMSAC方法可发现复杂形状的栅格簇,且算法时间复杂度低,需输入参数较少。  相似文献   

曲面位场的正则化线性规划法直接反演技术   总被引：4，自引：0，他引：4  

刘展  王万银 《地质与勘探》1999,35(6):62-66

讨论了可用于起伏地形上重磁位场数据直接反演的、正则化的线性规划反演方法,给出了求解模型、求解方法及相关的技术措施。通过理论模型试算,证明了方法的可行性,在某铜镍矿区的应用验证了方法的实用性。  相似文献   

Gender and Individual Access to Urban Opportunities: A Study Using Space–Time Measures     

Mei-Po Kwan 《The Professional geographer》1999,51(2):210-227

Conventional accessibility measures based on the notion of locational proximity ignore the role of complex travel behavior and space–time constraints in determining individual accessibility. As these factors are especially significant in women's everyday lives, all conventional accessibility measures suffer from an inherent “gender bias.” This study conceptualizes individual accessibility as space–time feasibility and provides formulations of accessibility measures based on the space–time prism construct. Using a subsample of European Americans from a travel diary data set collected in Franklin County, Ohio, space–time accessibility measures are implemented with a network-based GIS method. Results of the study indicate that women have lower levels of individual access to urban opportunities when compared to men, although there is no difference in the types of opportunities and areas they can reach given their space–time constraints. Further, individual accessibility has no relationship with the length of the commute trip, suggesting that the journey to work may not be an appropriate measure of job access.  相似文献   

Dynamics of three-block assemblies with unilateral deformable contacts. Part 1: contact modelling     

Ugo Andreaus  Paolo Casini 《地震工程与结构动力学》1999,28(12):1621-1636

As far as the dynamics of multibody systems is concerned, a brief review has been performed in order to frame the dynamic response of a trilith (the simplest scheme of a colonnade belonging to a temple) into a wide theoretical background. Under the assumption of rigid bodies, two different approaches can be found in the literature: rigid or deformable contacts formulation. In this paper, an effort is made at outlining the principle of rigid contact formulation and of deformable contact formulation. The latter approach can be assumed within the framework of the distinct element method; for this purpose a model of deformable contact has been proposed in order to simulate the real behaviour of stone joints. The sample application referred to the trilith will be presented in Part 2. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Can climate variability information constrain a hydrological model for an ungauged Costa Rican catchment?          下载免费PDF全文

Beatriz Quesada‐Montano  Ida K. Westerberg  Diana Fuentes‐Andino  Hugo G. Hidalgo  Sven Halldin 《水文研究》2018,32(6):830-846

Long‐term hydrological data are key to understanding catchment behaviour and for decision making within water management and planning. Given the lack of observed data in many regions worldwide, such as Central America, hydrological models are an alternative for reproducing historical streamflow series. Additional types of information—to locally observed discharge—can be used to constrain model parameter uncertainty for ungauged catchments. Given the strong influence that climatic large‐scale processes exert on streamflow variability in the Central American region, we explored the use of climate variability knowledge as process constraints to constrain the simulated discharge uncertainty for a Costa Rican catchment, assumed to be ungauged. To reduce model uncertainty, we first rejected parameter relationships that disagreed with our understanding of the system. Then, based on this reduced parameter space, we applied the climate‐based process constraints at long‐term, inter‐annual, and intra‐annual timescales. In the first step, we reduced the initial number of parameters by 52%, and then, we further reduced the number of parameters by 3% with the climate constraints. Finally, we compared the climate‐based constraints with a constraint based on global maps of low‐flow statistics. This latter constraint proved to be more restrictive than those based on climate variability (further reducing the number of parameters by 66% compared with 3%). Even so, the climate‐based constraints rejected inconsistent model simulations that were not rejected by the low‐flow statistics constraint. When taken all together, the constraints produced constrained simulation uncertainty bands, and the median simulated discharge followed the observed time series to a similar level as an optimized model. All the constraints were found useful in constraining model uncertainty for an—assumed to be—ungauged basin. This shows that our method is promising for modelling long‐term flow data for ungauged catchments on the Pacific side of Central America and that similar methods can be developed for ungauged basins in other regions where climate variability exerts a strong control on streamflow variability.  相似文献   

基于局部相关性约束的三维大地电磁数据和重力数据的联合反演   总被引：4，自引：3，他引：1       下载免费PDF全文

殷长春  孙思源  高秀鹤  刘云鹤  陈辉 《地球物理学报》2018,61(1):358-367

为解决地球物理反演中多解性的问题,综合多种地球物理信息的联合反演受到了广泛的关注.本文依据不同地球物理响应可能由相同异常体引起,而不同地球物理分布参数之间存在相关性等特点,提出了一种基于局部Pearson相关系数约束的联合反演方法.该方法假设每个局部区域模型参数的分布具有线性相关特性,在拟合不同类型观测数据时,对局部模型参数施加相关性约束,进行联合反演以减少多解性.本文采用交替迭代联合反演流程,改善了同一目标函数下联合反演收敛性和速度问题.基于新的联合反演方法和流程,我们测试了三维大地电磁和重力仿真数据的联合反演.结果表明,本文提出的基于局部相关性约束的联合反演方法,能充分利用大地电磁和重力观测数据信息,有效改善单一地球物理反演收敛性和多解性的问题,反演效果得到明显提升.  相似文献   

基于地质体空间位置优化约束的航空重力梯度数据三维物性反演   总被引：1，自引：0，他引：1       下载免费PDF全文

张楠  吴燕冈  周帅  孙鹏飞 《地球物理学报》2019,62(4):1515-1525

重力数据的物性反演面临着严重的多解性问题,降低多解性的有效手段是加入约束条件.而边界识别、深度估计及成像方法可获取地质体的水平位置、深度范围等几何参数信息,本文将基于数据本身挖掘的地质体几何参数信息约束到物性反演中,以降低反演的多解性.通过引入基于深度信息的深度加权函数及基于水平位置的水平梯度加权函数建立优化约束条件,有效地提高了反演结果的横向及纵向分辨率.重力梯度数据包含更多的地质体空间特征信息,将优化约束反演方法应用到全张量数据的反演中,模型试验表明本文方法反演结果与理论模型更加吻合.最后对美国路易斯安那州文顿盐丘实测航空重力梯度数据的应用表明,本文方法在其他地球物理、地质资料不足的情况下获得更可靠的反演结果.  相似文献   

地震作用下曲线梁桥结构响应及敏感性分析          下载免费PDF全文

游新  何睿华  吴刚  宋帅 《世界地震工程》2020,(1):118-124

为研究不同设计参数对曲线梁桥地震响应的影响以指导结构抗震设计,对不同支承约束曲线梁桥地震响应及地震需求敏感性进行分析。采用增量动力分析（IDA）方法对比分析了不同支承约束曲线梁桥的结构地震响应变化趋势;采用Tornado图形法对不同结构参数影响程度进行了排序,找出了对结构地震需求影响显著的参数。结果表明:采用板式橡胶支座桥梁因支座易发生滑移而导致上部结构位移较大,但降低了下部结构响应,设置固定墩后,下部结构损伤显著增加;对于采用板式橡胶支座和铅芯橡胶支座的曲线梁桥,墩高及跨径对墩底曲率需求影响较大,而对于固定墩为墩梁固结形式和采用盆式橡胶支座的曲线梁桥,跨径及跨数对墩底曲率需求影响较大;对于采用不同支承约束的曲线梁桥,墩高和曲率半径对桥台位移需求影响较大,仅次于地震动参数PGA。  相似文献   

利用ArcGIS模型构建器检查地理国情监测数据的约束关系     

张磊 《测绘与空间地理信息》2022,(2):154-155,160

从2016年起地理国情信息获取进入常态化监测阶段,地理国情监测成果已在众多领域得到应用,为生态文明、民生保障、应急救援、离任审计等提供重要保障.本文利用ArcGIS模型构建器对地理国情监测数据建立工作流,不仅能快速准确地检查出错误的约束关系,而且能重复检查不同的县域,为质检人员节省时间.  相似文献   

Exploring the cosmological model in f(R,Tϕ) gravity with observational constraints     

《New Astronomy》2024

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