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41.
地壳增生和成矿作用是矿床学研究的前沿领域; 东天山作为中亚造山带的重要组成部分,在晚古生代地壳演化过程中经历了板块俯冲、碰撞造山大规模走滑剪切和后造山演化阶段,在每个构造演化阶段都伴随有地壳增生和大量有用金属元素的堆积。按照地壳增生和成矿作用关系,研究区晚古生代主要有如下几种矿床类型: 1)晚泥盆世—早石炭世增生前形成的Cu Mo Au Ag矿床; 2)早石炭世增生前形成的Fe Cu Pb Zn矿床; 3)晚石炭世—早二叠世增生后形成的造山型Cu Ni PGE矿床; 4)晚石炭世—早二叠世增生后形成的造山型Au Cu矿床。上述矿床在形成过程中既有地壳的水平增生,也有地壳的垂向增生作用,已经构成了我国重要的内生金属矿床富集区。 相似文献
42.
滨海湿地位于海洋与陆地生态系统的交错过渡带,具有极高的生产力和光合固碳效率,是海岸带蓝色碳汇的重要组成部分。滨海湿地生产力不仅由芦苇、翅碱蓬、红树林等陆上植被提供,水体中浮游植物的光合固碳也是提供初级生产力的重要途径。以往较多的调查和研究集中在陆上植被,而对于滨海湿地水域浮游植物和底栖微藻的报道较少。近年来随着各国政府和学者对二氧化碳排放和气候变化的关注,滨海湿地多圈层生态系统的碳循环和碳汇过程成为研究热点,而湿地水域生产力和光合固碳过程作为多圈层碳循环中重要的一个环节亦应受到足够的重视。以中国北方典型的盐沼湿地区域——辽河三角洲滨海湿地为案例,对湿地水域生产力研究进展进行综述,并对其影响因素进行讨论,以期为国家碳循环与碳中和目标调查提供参考资料。 相似文献
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Wave overtopping nearshore coastal structures, such as shore-parallel breakwaters, can significantly alter the current circulation and sediment transport patterns around the structures, which in turn affects the formation of tombolos and salients in the nearshore area. This paper describes the implementation of a wave overtopping module into an existing depth-averaged coastal morphological mode: COAST2D and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore-parallel breakwaters. The hydrodynamic aspects of the model were validated against a series of laboratory conditions. The model was then applied to a study site at Sea Palling, Norfolk, UK, where 9 shore-parallel segmented breakwaters including 4 surface-piercing and 5 low-crested breakwaters are present, for the storm conditions in Nov 2006. The model results were compared with laboratory data and field measurements, showing a good agreement on both hydrodynamics and morphological changes. Further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation, sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro-tide conditions. The results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures. 相似文献
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Starting with analysis on the evolving course of oasis and the characteristics and evolution of transitional zone between oasis and desert, in consideration of ecological elements including plant stomata resistance, area covered by vegetation, and physical elements including albedo of vegetation and bare soil, atmosphere temperature, and humidity, under the condition of the balance among net radiation flux, latent heat flux, and sensible heat flux, the following are calculated: temperatures of vegetation and bare soil in different conditions, as well as the evapotranspiration rate of ecosystem. Analysis on evapotranspiration rate indicates that it depends on both the climate of environment and the physiological and ecological conditions of plants. On certain conditions, the evapotranspiration rate of transitional zone between oasis and desert (i.e. area covered by vegetation less than 20%), in some parameter domains, appears in bifurcation or multiequilibrium state. Meanwhile, in such area, ecosystem is extremely unstable. Any minor change to the balance will cause either increase or reduction of area covered by vegetation in ecosystem, on the basis of discussion on the emergency of these phenomena. This paper is attempting to propose an effective way of destruction and rebuilt ecosystem in transitional zone. The way is to control the evaporation of plant through selecting anti-drought country plant with big stomata resistance, and modify the roughness of the underlying surface in ecosystem by establishing rational interspace structure of plant community, so as to put the degenerative ecosystem into the natural succession track. This primary theory is being verified through observation and analysis on historical data. 相似文献
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对于含多资料三维分潮波模型建立了一种岸边资料运动学外推的潮波第一边值方法,并对渤海的四大原湖波进行试算。结果证实本方法可行,该方法使潮波方程既满足第一边值问题,充分利用岸边测站资料,又保证岸界法向流速为零条件,符合物理意义。并对复型病态矩阵的收敛问题提出了一种可行性处理。 相似文献
49.
We investigate the behaviour of galaxy clustering on large scales using the PSC z catalogue. In particular, we ask whether there is any evidence of large-scale fractal behaviour in this catalogue. We find the correlation dimension in this survey varies with scale, consistent with other analyses. For example, our results on small and intermediate scales are consistent those obtained from the QDOT sample, but the larger PSC z sample allows us to extend the analysis out to much larger scales. We find firm evidence that the sample becomes homogeneous at large scales; the correlation dimension of the sample is D 2 =2.992±0.003 for r >30 h −1 Mpc. This provides strong evidence in favour of a universe that obeys the cosmological principle. 相似文献
50.
We investigate the electronic structures of one and two monolayer iron phthalocyanine (FePc) molecules on Au(111) surfaces. The first monolayer FePc is lying flat on the Au(111) substrate, and the second monolayer FePc is tilted at ~15° relative to the substrate plane along the nearest neighbour [101-] direction with a lobe downward to the central hole of the unit cell in the first layer. The structural information obtained by first-principles calculations is in agreement with the experiment results. Furthermore, it is demonstrated that the electronic structures of FePc molecules in one-monolayer FePc/Au(111) system are perturbed significantly, while the electronic structures of FePc molecules in the second monolayer in two-monolayer FePc/Au(111) system remain almost unchanged due to the screening of the buffer layer on Au(111). 相似文献