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Jean Paul Dubois 《Aquatic Sciences - Research Across Boundaries》1994,56(1):70-79
Helophytes are often incorporated into biological wastewater treatment plants. In favourable situations, they can take up large amounts of nutrients. One helophyte, the reed canarygrass (Phalaris arundinacea L.), is fast growing when supplied with sufficient light and nutrients. Experiments were carried out under natural climatic conditions in small plastic tanks filled with sand with regular additions of a balanced and concentrated nutrient solution. In the growing season (May–October), plant production reached 10.5 kg m–2 of dry biomass, of which 66% was in the aerial parts. Maximum nutrient uptake capacity was reached just after flowering and before senescence (beginning of October): 49% N, 34% P, 52% K and 34% Mg of the input was fixed in the aerial parts, which are easily harvestable. The corresponding values for the below ground parts were 12%, 10%, 11% and 11% respectively. Excretion of K and Mg has been observed when nutrients are translocated to the storage organs. 相似文献
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圆陀角地处长江北支与江苏海岸的交汇处,发育了典型的粉砂淤泥质潮滩,潮滩沉积物元素可记录海岸环境变化的信息。在圆陀角附近潮滩采集了长度为218 cm的YY孔岩芯,常量与微量元素分析结果显示,岩芯沉积物平均粒径与大多数元素之间相关性好,“粒控效应”特征明显。除Ca、Na、Ti、P、Sr外,岩芯大部分元素含量自下向上呈现由低变高再变低的趋势,并在岩芯132 cm深度出现最大值。根据圆陀角附近海岸沙嘴长江北支变迁的证据,苏北岸外海域是长江北支的重要泥沙来源;粒度和粘土校正后的元素含量呈自下而上由低变高的趋势。邻近区域沉积物元素富集系数分析显示,在1956年前后,圆陀角附近潮滩沉积物发生了较大的变化,1956年以前的主要来源于长江,1956年以后演变为主要来源于南黄海辐射沙洲南翼。 相似文献
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本文依据鸭绿江口主汊道采集的K1和K12柱状样,进行了常量元素的富集特征、相关系数、主成分分析及含量与特征参数垂向分布的讨论。研究表明:鸭绿江口属于涨潮三角洲,纳潮海湾泥质堆积区快速沉积的时间始于1960年。主汊道的沉积物具有多源性,K12柱状样受粒度控制显著,陆源碎屑为主;K1柱状样受粒度控制不显著,受海洋作用的影响较大。主汊道的沉积记录以1978年为界,分为上下2个沉积单元。主汊道的沉积物受到河口区水动力的强烈改造,与物源区的沉积物相比已经产生了很多的分异和变化。该研究通过对鸭绿江口主汊道常量元素沉积记录的分析,发现了近百年来该区域地貌演变和发育的规律,有效补充了鸭绿江口新生陆地形成过程的全貌。 相似文献
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Numerous research studies have proved that numerical models aiming at an accurate evaluation of the seismic response of RC framed buildings cannot ignore the inelastic behaviour of infills and the interaction between infill and frame elements. To limit the high computational burden of refined non-linear finite element models, in the latest decades, many researchers have developed simplified infill models by means of single or multiple strut-elements. These models are low time-consuming and thus adequate for static and dynamic analyses of multi-storey structures. However, their simulation of the seismic response is sometimes unsatisfying, particularly in the presence of infill walls with regular or (particularly) irregular distributions of openings. This paper presents a new 2D plane macro-element, which provides a refined simulation of the non-linear cyclic response of infilled framed structures at the expense of a limited computational cost. The macro-element consists of an articulated quadrilateral panel, a single 1D diagonal link, and eight 2D links and is able to model the shear and flexural behaviour of the infill and the non-linear flexural/sliding interaction between infill and surrounding frame. The proposed macro-element has been implemented into the open source software OpenSees and used to simulate the response of single-storey, single-span RC infilled frame prototypes tested by other authors. The above prototypes are selected as made of different masonry units and characterised by full or open geometric configuration. 相似文献
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