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51.
萨拉乌苏河流域150 ka BP以来的粒度旋回 总被引:18,自引:1,他引:18
萨拉乌苏河流域米浪沟湾地层剖面150kaBP以来古流动砂丘砂与河湖相和古土壤在粒度上具有多次显著的粗细韵律交替变化,粒度参数-Mz、σ、Sk、Kg和SC/D亦随之响应为多波动峰谷交替的态势,同时,粒度特征值-φ5、φ16φ、φ25、φ50、φ84、φ9相应地表现为非常有节奏地跳动,据此,将米浪沟湾剖面划分为27个粒度粗细沉积旋回,并认为其是150kaBP以来在东亚冬夏古代季风交替影响下沙漠演变的一个颇为完整的气候-地质过程记录。 相似文献
52.
三角网格模型剖分方法的研究与应用 总被引:1,自引:0,他引:1
数值波场正演在地震学和勘探地球物理学领域正得到越来越广泛的应用,用一个好的方法来建立一个复杂的地质模型则显得尤为关键。三角网格模型相对于层状模型和矩形网格模型在反映地质界面形态、三角网格剖分个数调节及射线追踪速度等方面具有明显优势。利用三角网格剖分的建模方法,在VC2008编程环境下实现了复杂地质模型的描述。通过对复杂模型的建模测试,表明采用三角网格剖分方法,可解决以下模型难题:①对复杂模型界面的描述;②对复杂逆断层的描述;③对封闭块体的描述;④对模型弹性参数进行描述。 相似文献
53.
According to the meteorological observation data of 72 stations from 1960 to 2010 in the Huanghe (Yellow) River Watershed, China, the long-term variations of potential evapotranspiration, calculated in the modified Penman-Monteith model of Food and Agriculture Organization of the United Nations, were presented, as well as the meteorological causes for the decrease of potential evapotranspiration were discussed. Since 1960, temperature has risen significantly and potential evapotranspiration a decreasing trend, which indicated the existence of "Evaporation paradox" in the Huanghe River Watershed. This phenomenon was not consistent spatially or temporally with the increase of temperature, potential evapotranspiration decreased in spring, summer and winter, mainly over most parts of Shanxi and Henan, and some parts of Gansu, Ningxia, Inner Mongolia, and Shaanxi. During the recent half century, the trends of temperature and potential evapotranspiration were negatively correlated at most of the stations, while precipitation and potential evapotranspiration exhibited a contrary trend. Calculated in multiple regressions, the contribution to potential evapotranspiration change of related meteorological factors was discussed, including mean pressure, maximum and minimum temperature, sunshine hours, relative humidity and average wind speed. The decrease of wind speed in the Huanghe River Watershed may be the dominating factor causing potential evapotranspiration decreasing. 相似文献
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The Ecological-living-productive land(ELPL) classification system was proposed in an effort to steer China's land pattern to an ecological-centered path, with the development model shifting from a single function into more integrated multifunction land use. The focus is coordinating the man-land contradictions and developing an intensive, efficient and sustainable land use policy in an increasingly tense relationship between humans and nature. Driven by socioeconomic change and rapid population growth, many cities are undergoing urban sprawl, which involves the consumption of cropland and ecological land and threatens the ecological balance. This paper aims to quantitatively analyze the critical effects of ELPL changes on eco-environmental quality according to land use classification based on leading function of ecology, living and production from 1990 to 2015 with a case study of Xining City. Also, four future land use scenarios were simulated for2030 using the Future Land Use Simulation(FLUS) model that couples human and natural effects. Our results show a decrease in productive land(PL) and an increase in ecological land(EL) and living land(LL) in Xining City. Forestry ecological land(FEL) covered the top largest proportion; agriculture productive land(APL) showed the greatest reduction and urban and rural living land(U-RLL) presented a dramatic increase. The eco-environmental quality improved in 1990-2010, mainly affected by the conversion of APL to FEL and GEL. However, the encroachment of U-RLL into APL, other ecological land(OEL) and FEL was the main contributor to the decline in eco-environmental quality in 2010-2015 as well as the primary reason for the increase area of lower-quality. The Harmonious Development(HD)-Scenario, characterized by a rational allocation of LL and PL and a better eco-environment, would have implications for planning and monitoring future management of ELPL, and may represent a valuable reference for local policy-makers. 相似文献
57.
Weidong Sun Jin-tuan Wang Li-peng Zhang Chan-chan Zhang He Li Ming-xing Ling Xing Ding Cong-ying Li Hua-ying Liang 《中国地球化学学报》2017,36(1):9-15
Copper is a moderately incompatible chalcophile element. Its behavior is strongly controlled by sulfides. The speciation of sulfur is controlled by oxygen fugacity. Therefore, porphyry Cu deposits are usually oxidized (with oxygen fugacities > ΔFMQ +2) (Mungall 2002; Sun et al. 2015). The problem is that while most of the magmas at convergent margins are highly oxidized, porphyry Cu deposits are very rare, suggesting that high oxygen fugacity alone is not sufficient. Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly (Lee et al. 2012; Wilkinson 2013). Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity (>ΔFMQ +2) may form magmas with initial Cu contents up to >500 ppm, favorable for porphyry mineralization. Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization. In contrast, re-melting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits. Thick overriding continental crust reduces the “leakage” of hydrothermal fluids, thereby promoting porphyry mineralization. Nevertheless, it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2–4 km where porphyry deposits form. 相似文献
58.
The heavy metal inventory and the ecological risk of the estuarine sediments in Hailing Bay, an important maricultural zone along the southern coast of China, were investigated. Results show that the surface sediments were mainly polluted by As (2.17-20.34 mg/kg), Ni (1.37-42.50mg/kg), Cu (1.21-58.84 mg/kg) and Zn (11.69-219.22 mg/kg). Furthermore, the aquafarming zone was significantly more polluted than the non-aquafarming zone, and cluster analysis suggested additional sources of heavy metal input in the aquafarming zone. As, Cr, Cu, Ni, Pb and Zn were mainly present in the non-bioavailable residual form in the surface sediments, whereas Cd was predominantly in the highly mobile acid soluble and reducible fractions. The ecological risk of the polluted sediments stemmed mainly from Cd, and from As, Cu and Pb to less degrees. The highest potential risks occurred near the aquaculture base, indicating the need to control heavy metal inputs from aquafarming activities. 相似文献
59.
融合遥感影像、社会开放大数据、统计资料等多源数据,以长沙市为例,围绕生态宜居、健康舒适、安全韧性、交通便捷、风貌特色、整洁有序、多元包容、创新活力等8个方面构建城市体检指标体系,运用归一法和层次分析法对城市自然本底和运行体征展开计算评估,结果发现:1)长沙市人居环境整体良好,城市生态宜居和整洁有序度较高,交通便捷和安全韧性建设亟需加强,风貌特色、健康舒适、创新活力、多元包容等仍有改善空间。2)各区县专题发展水平不均,在保留区域功能特色的基础上,应该着重解决发展的短板。3)城市中心城区人口密度、空气质量优良天数、万车死亡率等指标达到最高水平,但在便民服务设施完整覆盖度、住宅建筑更新和开发、群体包容等方面与城市发展需求还有一定差距。根据多源数据城市体检结果可知,长沙市未来需要以问题和需求为导向,精准治理“城市病”,努力提高城市居民生活满意度、幸福感和归属感。 相似文献
60.
Yakun He Wenhao Yu Xiang Zhang 《International journal of geographical information science》2017,31(8):1541-1561
Street patterns reflect the distribution characteristics of a street network and affect the urban structure and human behavior. The recognition of street patterns has been a topic of interest for decades. In this study, a linear tessellation model is proposed to identify the spatial patterns in street networks. The street segments are broken into consecutive linear units with equal length. We define five focal operations using neighborhood analysis to extract the geometric and topological characteristics of each linear unit for the purpose of grid-pattern recognition. These are then classified by Support Vector Machine, and the result is optimized based on Gestalt principles. The experimental results demonstrate that our method is effective for mining grid patterns in a street network. 相似文献