Chlorophyll production,in response to nutrient additions,by the algae in Lake Rotorua water     

E. White  G. W. Payne 《新西兰海洋与淡水研究杂志》2013,47(2):131-138

Batch cultures of water and algae from Lake Rotorua were subjected to nitrogen, phosphorus, and trace element additions, singly and in combination, at monthly intervals between June 1975 and May 1976. The algal responses to the additions were assayed after 5 d incubation, by extracting the chlorophyll from the algae and estimating the concentration by fluorescence. The chlorophyll production consistently responded positively to the addition of nitrogen, while responses to the addition of phosphorus and trace elements were minor by comparison. Although the chlorophyll responses to nitrogen may not have been paralleled by actual growth, the consistent pattern of behaviour by algae in the batch cultures was interpreted as evidence of persistent shortage of nitrogen in the Lake Rotorua environment.  相似文献   

Drained behaviour of Changi sand in triaxial and plane-strain compression     

《Geomechanics and Geoengineering》2013,8(1):29-39

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硫酸亚铁侵蚀红土的受力特性          下载免费PDF全文

王盼  黄英  刘鹏  邓欣  樊宇航 《水文地质工程地质》2013,40(4):112-116

针对云南典型红土,考虑硫酸亚铁的浓度和试样养护时间,采用击实、直剪、固结、渗透等试验方法,研究硫酸亚铁侵蚀红土的受力特性.结果表明:硫酸亚铁的侵蚀改变了红土的击实特性,存在最佳浸润时间.随硫酸亚铁浓度的增大,红土的最大干密度逐渐增大,最优含水率逐渐减小;随浸润时间的延长,最优含水率出现谷值,最大干密度出现谷值和峰值,浸润时间较短,最大干密度出现谷值;浸润时间较长,最大干密度出现峰值.硫酸亚铁浓度较低,养护时间较短,红土的抗剪强度和压缩模量出现峰值,压缩系数和渗透系数出现谷值;随浓度的增大和养护时间的延长,红土的抗剪强度和压缩模量逐渐减小,压缩系数和渗透系数逐渐增大.硫酸亚铁侵蚀红土受力特性的变化可以从硫酸亚铁的胶结作用和侵蚀作用两个方面来解释.  相似文献   

Experimental evaluation of rectangular reinforced concrete column behaviour under biaxial cyclic loading     

Hugo Rodrigues  António Arêde  Humberto Varum  Aníbal G. Costa 《地震工程与结构动力学》2013,42(2):239-259

The cyclic behaviour of reinforced concrete columns has been the subject of many experimental studies in recent years. However, most of these studies have focused on the unidirectional loading of columns with square cross‐sections under constant axial loading conditions. In the present study, four types of full‐scale quadrangular building columns were tested under different types of loading, including uniaxial and biaxial loading conditions. The first two specimens of each column type were independently cyclically tested in the strong and weak directions. Bidirectional tests using different loading paths were performed on the other column specimens. All columns were tested under constant axial loading conditions. In this paper, the experimental results are presented, and the global behaviour of tested columns is discussed, particularly focusing on the stiffness and strength degradation because of the increasing cyclic demand. Finally, the deformation‐based performance limits proposed in Part 3 of Eurocode 8 were calculated and compared with the experimental results. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Cyclic testing of a single bay reinforced concrete frames with various types of masonry infill     

Jurko Zovkic  Vladimir Sigmund  Ivica Guljas 《地震工程与结构动力学》2013,42(8):1131-1149

In this paper, a contribution of various types of masonry infill to the behaviour of reinforced concrete frames under lateral loads is presented. As a part of the bigger project, ten one‐bay, one‐storey reinforced concrete frames were designed according to the EC8, built in a scale 1:2.5, infilled with masonry and tested under constant vertical and cyclic lateral load. The masonry wall had various strength properties, namely, high strength hollow clay brick blocks, medium strength hollow clay brick blocks and low strength lightweight autoclaved aerated concrete blocks. There were no additional shear connectors between the masonry and frame. The results showed that the composite ‘framed wall’ structure had much higher stiffness, damping and initial strength than the bare frame structure. Masonry infill filled in the load capacity gap from very low (0.05%) to drifts when the frame took over (0.75%). The structures behaved as linear monolithic elements to drifts of 0.1%, reached the maximum lateral capacities at drift of 0.3%, maintained it to drifts of 0.75% and after that their behaviour depended on the frame. Masonry infill had severe damage at drift levels of about 0.75% but contributed to the overall system resistance to drifts of about 1%. At that drift level, the frame had only minor damage and was tested to drifts of about 2% without any loss of capacity. Improvement of the ‘infill provisions’ in the codes could be sought by taking into account the contribution of a common masonry that reduces expected damages by lowering the drift levels. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

An event-based conceptual model for context-aware movement analysis     

Gennady Andrienko  Natalia Andrienko  Marco Heurich 《International journal of geographical information science》2013,27(9):1347-1370

Current tracking technologies enable collection of data, describing movements of various kinds of objects, including people, animals, icebergs, vehicles, containers with goods and so on. Analysis of movement data is now a hot research topic. However, most of the suggested analysis methods deal with movement data alone. Little has been done to support the analysis of movement in its spatio-temporal context, which includes various spatial and temporal objects as well as diverse properties associated with spatial locations and time moments. Comprehensive analysis of movement requires detection and analysis of relations that occur between moving objects and elements of the context in the process of the movement. We suggest a conceptual model in which movement is considered as a combination of spatial events of diverse types and extents in space and time. Spatial and temporal relations occur between movement events and elements of the spatial and temporal contexts. The model gives a ground to a generic approach based on extraction of interesting events from trajectories and treating the events as independent objects. By means of a prototype implementation, we tested the approach on complex real data about movement of wild animals. The testing showed the validity of the approach.  相似文献   

Present-day sediment dynamics of the Sanaga catchment (Cameroon): from the total suspended sediment (TSS) to erosion balance     

J.R. Ndam Ngoupayou  J.G. Dzana  A. Kpoumie  R. Tanwi Ghogomu  A. Fouepe Takounjou  J.J. Braun 《水文科学杂志》2013,58(6):1080-1093

ABSTRACT

Total suspended sediment (TSS) data for 1960–1970 and from recent investigations (1990–2000) are used to evaluate the variability in sediment yield of the Sanaga catchment (Cameroon) and the equivalent rates of erosion. At the annual and seasonal time scales, total suspended sediment concentrations for the Mbam sub-catchment are three to four times higher than for the Sanaga basin, reflecting the higher sensitivity of the former to erosion. Classical clockwise hysteresis loops are observed in both sub-catchments, despite a significant increase in human-induced catchment changes. At the multi-year time frame (over a 40-year period), it appears that the second half of the 1990s is marked by a downward trend in TSS. This shift is due to the control infrastructures (river impoundments and ponds) installed in certain parts of the whole catchment, combined with a drop in annual rainfall and river discharge.