一个关于河口及浅海的三维分步杂交模型   总被引：1，自引：0，他引：1  

石磊 《中国海洋大学学报(自然科学版)》1996,(4)

根据分步杂交方法，构造出一个关于河口及浅海环境的三维分步杂交模型。在垂直结构上，本文引入了σ坐标，并在垂直方向上利用交错网格，在水平方向上利用三角形网格离散。本模型在时间上采用分步方法，在不同分步里，采用了与算子相适应的计算方法  相似文献   

地理国情普查数据在林地监测中的应用研究   总被引：1，自引：0，他引：1  

姜丽丽  刘红军 《测绘与空间地理信息》2017,(2):127-129

以黑龙江省穆棱市为研究区,利用2005年的基础地理信息数据和2015年全国地理国情普查数据成果作为基础数据,并结合SPOT-5、ZY-3卫星遥感影像数据,对穆棱市林地进行监测。本文从数据的收集与整理、影像处理和变化监测数据提取及处理方法等进行应用研究,准确快速获取变化信息的光谱、纹理、植被指数及面积等信息,通过特定运算得到每期研究区内植被的覆盖率、保有量以及蓄积量,实现林地覆盖率、保有量及蓄积量的动态变化监测。最后,通过对监测数据的统计分析得出穆棱市林地变化监测成果。  相似文献   

抚仙湖流域植被覆盖度时空分异及其与坡度的关系     

李石华  金宝轩  周峻松  王金亮  彭双云 《地域研究与开发》2017,36(3)

采用像元二分模型,以1974-2014年间的10期Landsat 5/8影像和DEM数据,对抚仙湖流域植被覆盖动态变化进行监测,并结合基础地理信息数据、行政区划界资料、行业部门专题资料等,分析流域植被覆盖时空分异及其与坡度的关系.结果表明:(1)1974-2014年,抚仙湖流域裸地(Ⅰ级)面积波动极小,低植被覆盖(Ⅱ级)、中低植被覆盖(Ⅲ级)、中高植被覆盖(Ⅳ级)面积变化波动大,变化趋势线数次出现谷值和峰值,高植被覆盖(Ⅴ级)面积则呈增加趋势.(2)坡度较小、地势较平缓的区域(0°~15°)以裸地和低植被覆盖为主;中低植被覆盖度、中高植被覆盖和高植被覆盖度主要分布在地势比较陡峭的区域(>15°).(3)抚仙湖流域各年份植被覆盖度Ⅰ级面积最大,1974,1977,1989,1996年Ⅱ,Ⅲ级面积较大,而Ⅳ,Ⅴ级面积较小;2000年后的Ⅱ,Ⅲ,Ⅳ级面积变化较小;2006,2009,2012,2014年Ⅳ,Ⅴ级的面积较大,Ⅱ,Ⅲ级的面积较小.  相似文献   

Geochemistry and Nd–Sr isotopic studies of Late Mesozoic granitoids in the southeastern Hubei Province, Middle–Lower Yangtze River belt, Eastern China: Petrogenesis and tectonic setting     

Guiqing Xie  Jingwen Mao  Ruiling Li  Frank P. Bierlein 《Lithos》2008,104(1-4):216-230

A geochemical and isotopic study was carried out for the Mesozoic Yangxin, Tieshan and Echeng granitoid batholiths in the southeastern Hubei Province, eastern China, in order to constrain their petrogenesis and tectonic setting. These granitoids dominantly consist of quartz diorite, monzonite and granite. They are characterized by SiO₂ and Na₂O compositions of between 54.6 and 76.6 wt.%, and 2.9 to 5.6 wt.%, respectively, enrichment in light rare earth elements (LREE) and large ion lithophile elements (LILE), and relative depletion in Y (concentrations ranging from 5.17 to 29.3 ppm) and Yb (0.34–2.83 ppm), with the majority of the granitoids being geochemically similar to high-SiO₂ adakites (HSA). Their initial Nd (ε_Nd = − 12.5 to − 6.1) and Sr ((⁸⁷Sr/⁸⁶Sr)_i = 0.7054–0.7085) isotopic compositions, however, distinguish them from adakites produced by partial melting of subducted slab and those produced by partial melting of the lower crust of the Yangtze Craton in the Late Mesozoic. The granitoid batholiths in the southeastern Hubei Province exhibit very low MgO ranging from 0.09 to 2.19 wt.% with an average of 0.96 wt.%, and large variations in negative to positive Eu anomalies (Eu/Eu = 0.22–1.4), especially the Tieshan granites and Yangxin granite porphyry (Eu/Eu = 0.22–0.73). Geochemical and Nd–Sr isotopic data demonstrate that these granitoids originated as partial melts of an enriched mantle source that experienced significant contamination of lower crust materials and fractional crystallization during magma ascent. Late Mesozoic granitoids in the southeastern Hubei Province of the Middle–Lower Yangtze River belt were dominantly emplaced in an extensional tectonic regime, in response to basaltic underplating, which was followed by lithospheric thinning during the early Cretaceous.  相似文献   

面向嵌入式GIS应用的地图标注算法设计与实现     

徐柳茂  张辉  蒋念东 《测绘科学》2008,33(5)

本文提出的一种基于栅格的地图标注算法,应用于嵌入式G IS系统中电子地图标注的自动配置。该算法将地图中各要素标注的自动配置作为一个统一的整体来对待,从而避免了一般局部标注配置算法可能终止于一个局部最优解的缺点。通过实例证明,利用该算法进行电子地图中标注的自动配置,数据计算量小,通用性强,速度较快。  相似文献   

Development of an establishment scheme for a DGVM     

Xiang Song  Xiaodong Zeng  Jiawen Zhu  Pu Shao 《大气科学进展》2016,33(7):829-840

Environmental changes are expected to shift the distribution and abundance of vegetation by determining seedling establishment and success. However, most current ecosystem models only focus on the impacts of abiotic factors on biogeophysics (e.g., global distribution, etc.), ignoring their roles in the population dynamics (e.g., seedling establishment rate, mortality rate, etc.) of ecological communities. Such neglect may lead to biases in ecosystem population dynamics (such as changes in population density for woody species in forest ecosystems) and characteristics. In the present study, a new establishment scheme for introducing soil water as a function rather than a threshold was developed and validated, using version 1.0 of the IAP-DGVM as a test bed. The results showed that soil water in the establishment scheme had a remarkable influence on forest transition zones. Compared with the original scheme, the new scheme significantly improved simulations of tree population density, especially in the peripheral areas of forests and transition zones. Consequently, biases in forest fractional coverage were reduced in approximately 78.8% of the global grid cells. The global simulated areas of tree, shrub, grass and bare soil performed better, where the relative biases were reduced from 34.3% to 4.8%, from 27.6% to 13.1%, from 55.2% to 9.2%, and from 37.6% to 3.6%, respectively. Furthermore, the new scheme had more reasonable dependencies of plant functional types (PFTs) on mean annual precipitation, and described the correct dominant PFTs in the tropical rainforest peripheral areas of the Amazon and central Africa.  相似文献   

Uncertainty,entropy, scaling and hydrological stochastics. 2. Time dependence of hydrological processes and time scaling / Incertitude,entropie, effet d'échelle et propriétés stochastiques hydrologiques. 2. Dépendance temporelle des processus hydrologiques et échelle temporelle     

《水文科学杂志》2013,58(3)

Abstract

The well-established physical and mathematical principle of maximum entropy (ME), is used to explain the distributional and autocorrelation properties of hydrological processes, including the scaling behaviour both in state and in time. In this context, maximum entropy is interpreted as maximum uncertainty. The conditions used for the maximization of entropy are as simple as possible, i.e. that hydrological processes are non-negative with specified coefficients of variation and lag-one autocorrelation. In the first part of the study, the marginal distributional properties of hydrological processes and the state scaling behaviour were investigated. This second part of the study is devoted to joint distributional properties of hydrological processes. Specifically, it investigates the time dependence structure that may result from the ME principle and shows that the time scaling behaviour (or the Hurst phenomenon) may be obtained by this principle under the additional general condition that all time scales are of equal importance for the application of the ME principle. The omnipresence of the time scaling behaviour in numerous long hydrological time series examined in the literature (one of which is used here as an example), validates the applicability of the ME principle, thus emphasizing the dominance of uncertainty in hydrological processes.  相似文献   

湖南金船塘矿区矽卡岩矿物及Sn元素在绿帘石中的分布特征   总被引：3，自引：0，他引：3  

刘惠芳  陆琦 《地球科学》2008,33(2):210-218

金船塘矿区位于千里山花岗岩岩体西侧, 与东侧柿竹园矿区均是湖南柿竹园特大型W-Sn-Mo-Bi矿床目前正在开采的重要矿区.该矿区块状矽卡岩的矿物特点是: 石榴子石以钙铝石榴子石为主, 辉石存在透辉石-钙铁辉石连续系列, 长石以钙长石大量产出为特点, 硅灰石出现了不常见的锰铁硅灰石; 绿帘石中普遍含Sn, SnO₂含量0.2%~2%.根据绿帘石中Sn元素的详细测定和计算, 查明Sn元素在绿帘石中含量与在矿物中位置具幂律函数关系, 计算的分形维为1.93, 从矿物微观的尺度确认Sn等成矿元素在运移和分布上具分形时-空结构, 从而证实自组织的临界状态是柿竹园特大型多金属矿床动力学的基本特点.   相似文献   

Numerical investigation of apparent multifractality of samples from processes subordinated to truncated fBm     

Alberto Guadagnini  Shlomo P. Neuman  Monica Riva 《水文研究》2012,26(19):2894-2908

We investigate numerically apparent multi‐fractal behavior of samples from synthetically generated processes subordinated to truncated fractional Brownian motion (tfBm) on finite domains. We are motivated by the recognition that many earth and environmental (including hydrological) variables appear to be self‐affine (monofractal) or multifractal with Gaussian or heavy‐tailed distributions. The literature considers self‐affine and multifractal types of scaling to be fundamentally different, the first arising from additive and the second from multiplicative random fields or processes. It has been demonstrated theoretically by one of us that square or absolute increments of samples from Gaussian/Lévy processes subordinated to tfBm exhibit apparent/spurious multifractality at intermediate ranges of separation lags, with breakdown in power‐law scaling at small and large lags as is commonly exhibited by real data. A preliminary numerical demonstration of apparent multifractality by the same author was limited to Gaussian fields having nearest neighbor autocorrelations and led to rather noisy results. Here, we adopt a new generation scheme that allows us to investigate apparent multifractal behaviors of samples taken from a broad range of processes including Gaussian with and without symmetric Lévy and log‐normal (as well as potentially other) subordinators. Our results shed new light on the nature of apparent multifractality, which has wide implications vis‐a‐vis the scaling of many hydrological as well as other earth and environmental variables. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Secondary consolidation of clay as an anomalous diffusion process     

Philippe Cosenza  Dean Korošak 《国际地质力学数值与分析法杂志》2014,38(12):1231-1246

Secondary consolidation of clay soil is considered as a result of anomalous diffusion of pore water pressure from the micropores to the macropores. By using simplified pore geometry, a heuristic approach allows us to infer the expression of the associated rate of vertical secondary deformation written as a fractional derivative of the pore pressure. The insertion of this expression into the 1D Terzaghi's theory leads to a particular type of time‐fractional diffusion equation of the pore pressure that is solved semi‐analytically. The advantage of such theoretical approach stems from the concise and compact way of treating the secondary consolidation. Only two additional parameters are needed: the fractional order, ν, and the fractional viscosity factor, θ, both accounting for the physicochemical interactions between pore fluid and clay particles. This theoretical approach is tested on experimental data obtained from the Cubzac‐les‐Ponts clay soil intensively studied for secondary consolidation. This application shows a good agreement between the data and the predicted values confirming the interest of the initial assumption and the use of the fractional derivatives formalism. Moreover, good correlations between the inverted fractional parameters and the empirical secondary consolidation index C_α measured independently are obtained: the fractional order ν, if experimentally calibrated, can be used as a reasonable estimator of the slope of the secondary consolidation portion of consolidation curve. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献