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81.
Measuring spatial concentration is a key problem when studying geographical phenomena in many areas, including economic activities, atmospheric pollution, animal habitats, and so on. Two important aspects related to the measurement of spatial concentration are data variability and spatial autocorrelation. Rather than combining different indicators for each of these characteristics, this article proposes a new indicator based on the reconstruction of local spatial decompositions of the classical Gini coefficient. A Monte Carlo simulation study is conducted to evaluate the properties of the new indicator, and the results demonstrate that the indicator is highly linearly correlated with both spatial autocorrelation and data dispersion. Moreover, its elasticities to either the spatial autocorrelation or data dispersion are extremely close to 1 under various experimental circumstances. These findings indicate that the new indicator can reflect not only the absolute level of but also the change in spatial concentration effectively. Applying the indicator to the per capita gross domestic product data set for the middle reach of the Yangtze River, we also demonstrate that the new indicator and its local components are easy to implement and are useful in local spatial association analyses. 相似文献
82.
基于1993-2008 年间4 个时相的遥感影像,应用SLEUTH模型模拟与预测自组织和规划引导两类情景下泉州中心城区的城市用地增长过程,并借助空间关联法分析其城市增长的空间格局演化特征,为“两规”空间协调提供科学依据。结果表明:① SLEUTH模型适用于研究区的城市增长模拟与预测,其对城市用地扩展的数量拟合要优于空间匹配,可作为多方案情景模拟的一个技术手段。② 规划引导预案的MPS、ED、AWMSI、MPI 四类景观指数均优于自组织预案,城市用地斑块的整体性、连接性较优,未来城市发展较为紧凑,利于实现土地的集约利用与城市的集聚发展。③ 随预测时间推移,研究区城市用地扩展的速率以及空间集聚性将有所减弱,城市增长的热点区也会发生演变与迁移。2008-2020 年,热点区分布总体呈现“圈层式”结构,局部以“跨江发展”为主要特征;2020-2030 年,热点区总体布局较为发散,局部则呈“环湾发展”与“孤立分布”特征。本研究将情景模拟、景观指数、空间分析等方法有效结合,有助于深刻理解研究区的城市空间增长过程,可为城市管理工作提供决策支持。 相似文献
83.
北斗卫星系统是中国正在实施的自主研发、独立运行的卫星定位与通信系统.因其具有短报文通信功能,进行相应的软硬件开发,可以用于传输包括烈度在内的强震动台网观测数据.通过北斗卫星传输烈度速报的性能测试和在芦山7.0级大地震中的实际应用效果,对北斗卫星系统目前在强震动台网数据传输中的应用方式和效能进行介绍. 相似文献
84.
MODIS NDVI和AVHRR NDVI 对草原植被变化监测差异 总被引:5,自引:0,他引:5
以草地作为研究载体,对比分析草原植被AVHRR NDVI和MODIS NDVI两种NDVI序列的年内、年际变化特征,讨论两种NDVI序列对降水量、平均气温和水汽压3种气候因子的响应差异,为合理选择NDVI序列对植被进行监测研究提供参考。结果表明:(1)两种NDVI序列所反映的草原植被年内变化趋势相似,但MODIS NDVI对各类草原的区分度优于AVHRR NDVI;(2)两种NDVI序列所反映的2000年—2003年草原植被年际变化差异明显。较之于MODIS NDVI,AVHRR NDVI变化趋势分类图表现出更强的植被改善趋势,植被改善面积在AVHRR NDVI变化趋势分类图中占94.25%,在MODIS NDVI中为83.33%;两种NDVI变化趋势分类图反映的植被变化趋势吻合度为52.88%。(3)两种NDVI序列与水汽压、降水量相关性差异显著。MODIS NDVI与各站点平均气温的相关系数均大于GIMMS NDVI;而MODIS NDVI与水汽压的相关系数83%(10个站点)小于GIMMS NDVI,与降水量的相关系数67%(8个站点)小于GIMMS NDVI。 相似文献
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87.
Mineralogy,major and trace element geochemistry of riverbed sediments in the headwaters of the Yangtze,Tongtian River and Jinsha River 总被引:1,自引:0,他引:1
Weihua Wu Shijun Xu Huayu Lu Jiedong Yang Hongwei Yin Wen Liu 《Journal of Asian Earth Sciences》2011,40(2):611-621
We collected riverbed sediments of the headwaters of the Yangtze River (Chumaer River, Tuotuo River, Gaerqu River and Buqu River), Tongtian River and Jinsha River (HTJR) flowing on the eastern Tibetan Plateau and analyzed their mineralogical features, major and trace element contents. The results show: (i) very poor correlations of Na2O, K2O, CaO, Ba, and Sr to SiO2, LREE to Th, HREE to Hf, and Ta/La to Ti, and characteristics of Eu anomaly (the ratios of (Eu/Eu*)N range from 0.60 to 0.83 with an average value of 0.71) all indicate that the Jinsha River sediments have not undergone much mineralogical sorting; (ii) illite and chlorite are predominant clay minerals, and quartz, calcite, dolomite, albite, and K-feldspar are prevailing non-clay minerals. The characteristics of mineral assemblage indicate relatively weak chemical weathering degree in these river basins; (iii) very high contents of Fe2O3, MgO, TiO2, Sc, V, Cr, Co, and Ni at Panzhihua mainly result from the huge-sized V–Ti magnetite deposits occurred in layered gabbroic intrusion; and (iv) the chemical alteration index (CIA) in the HTJR ranges from 46.5 to 69.2 and with an average value of 60.5 which indicates relatively weak weathering degree. 相似文献
88.
89.
Food security has drawn great attention from both researchers and practitioners in recent years. Global warming and its resultant extreme drought events have become a great challenge to crop production and food price stability. This study aimed to establish a preliminary theoretical methodology and an operational approach for assessing the physical vulnerability of two wheat varieties (“Yongliang #4” and “Wenmai #6”) to agricultural drought using Environmental Policy Integrated Climate model (EPIC). Drought hazard index was set up based on output variables of the EPIC water stress (WS), including the magnitude and duration of WS during the crop-growing period. The physical vulnerability curves of two wheat varieties to drought were calculated by the simulated drought hazard indexes and loss ratios. And the curve’s effect on drought disaster risk was defined as A, B and C sections, respectively. Our analysis results showed that (a) physical vulnerability curves varied between two wheat varieties, which were determined by genetic parameters of crops; (b) compared with spring wheat “Yongliang 4#” winter wheat “Wenmai 6#” was less vulnerable to drought under the same drought hazard intensity scenario; (c) the wheat physical vulnerability curve to drought hazard displayed a S shape, suggesting a drought intensity–dependent magnifying or reducing effect of the physical vulnerability on drought disasters; (d) the reducing effect was mainly in the low-value area of vulnerability curve, whereas the magnifying effect was in the middle-value area, and the farming-pastoral zone and the Qinling Mountain–Huaihe River zone formed important spatial division belts. 相似文献
90.
Major element geochemistry of purple soils/rocks in the red Sichuan Basin, China: implications of their diagenesis and pedogenesis 总被引:1,自引:0,他引:1
Jing Du Youjin Luo Weihua Zhang Chang Xu Chaofu Wei 《Environmental Earth Sciences》2013,69(6):1831-1844
Major element compositions and chemical weathering features of the purple soils and their corresponding rocks in the Red Sichuan Basin, China were studied in this paper to infer the diagenetic features of the purple rocks and the pedogenetic features of the purple soils. The results showed that all of the rock and soil samples, except those from Yibin, have strongly similar major element compositions and the distribution patterns of their major element compositions are similar to those of the upper continental crust. Chemical index of alteration, chemical index of weathering and Na2O/K2O indicate that the purple soils and rocks have similar chemical weathering intensities, whereas the Al2O3–CaO* + Na2O–K2O (A–CN–K) relationship, suggests that chemical weathering was strong during diagenesis of the purple rocks, but weak during pedogenesis of the purple soils. Variations in major element compositions of the purplish rock samples, except that from Yibin, do not primarily reflect differences in compositions of the sediment source, sediment recycling and potassium metasomatism, and therefore the effects of chemical weathering on the major element compositions were mainly dependent on climate condition and the residence time of material exposed to chemical weathering. Chemical weathering of the purple rocks reached only moderate degrees under the general influence of warm and humid climate during Jurassic and Cretaceous. Warmer and more humid climate conditions partly resulted in stronger chemical weathering of rocks in the southern region of the basin than in the central and western region, whereas shorter residence time of material in upslope position partly resulted in weaker chemical weathering of rocks in the eastern region than in the central and western region. The same climate and stable tectonic setting led to comparable chemical weathering intensities of rocks in the Ziliujing and Jiaguan Formations. Gradually colder and dryer climate from Early Jurassic to Middle Jurassic then to Late Jurassic and shorter residence time in tectonically active setting of Middle Jurassic and late Late Jurassic resulted in the following order of chemical weathering intensity of the purple Jurassic rocks: Ziliujing Formation ? Shaximiao Formation ≈ Suining Formation > Penglaizhen Formation. 相似文献