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Natural Resources Research - An accurate forecasting model for the price volatility of minerals plays a vital role in future investments and decisions for mining projects and related companies. In...  相似文献   
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The Sanyangzhuang site, Henan Province, China, has a 12‐m‐deep stratigraphic sequence with remains from the Tang (A.D. 618–907), late Western Han (ca. 140 B.C.–A.D. 23), Warring States (475–221 B.C.), Late Neolithic or Early Bronze Age (ca. 5000–1500 B.C.), Middle Holocene, and Early Holocene times. All of the paleosols are deeply buried. We investigate four issues relevant to the archaeology of the lower Yellow River Valley. First, we confirm that the Yellow River flowed north toward Bohai Bay throughout most of the Holocene. Second, we expand understanding of Holocene paleoenvironments. Long episodes of landscape stability punctuated by brief periods of Yellow River flooding represent the dominant environmental pattern. Third, we investigate how the complex relationships between climate, culture, and the environment affect Yellow River flooding, which in turn shapes Chinese civilization and history. Flooding in late Western Han times affected a vast area of north‐central China; this catastrophe contributed to the downfall of the late Western Han Dynasty. Finally, this research sheds light on the role of Yellow River alluviation in site burial and preservation. Rapid alluviation in the region has buried many archaeological sites. Settlement pattern research needs to take seriously the limitations placed on site visibility in quickly aggrading floodplains. However, gentle alluviation has also preserved settlements and entire landscapes providing unparalleled opportunities to explore the archaeological and historical record of the lower Yellow River Valley.  相似文献   
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瞿海旺  范荣双  徐然 《测绘科学》2016,41(6):102-107
针对传统的射线追踪算法在三维城市环境下存在海量计算、效率低下的问题,该文提出基于城市布局分区、降维、朝向测试、加速多镜法相结合的射线追踪算法。针对各个城市不同的布局特点对地理空间进行区域划分,构建空间索引,排除大量与射线追踪无关的城市建构筑物;同时采用降维处理、朝向测试、加速多镜像相结合的方式,减少空间几何计算的次数,从而提高计算的效率。将该算法与信号覆盖预测理论相结合,实现了点对点的信号准确计算。基于城市移动多媒体的预测结果表明:该算法可以准确、快速地实现城市的区域场强计算。  相似文献   
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