基于水华爆发的水源地安全模糊评价

根据水源地频发的水华爆发现象,采用故障树分析法,分析导致水源地水华爆发的原因.根据故障树分析结果,结合2010—2011年东营市某水源地水源数据资料,建立评价指标体系.采用模糊综合评价分析法,从水华爆发的角度对东营市某水源地进行安全评价,最终确定该水源地的安全等级.     

Changes in phytoplankton composition in a Mediterranean coastal lagoon in the Cullera Estany (Comunitat Valenciana,Spain)

The Cullera Estany is a coastal lagoon located in a highly intensified agriculture and tourist area in Valencia. This coastal lagoon has connections with the sea that produce marine intrusion and generate a freshwater interface. Four sampling campaigns were carried out during 2010 in order to analyse the phytoplankton composition and its relation to nutrient content through a Redundancy Analysis. Temperature, dissolved oxygen, nitrite and salinity are the main factors controlling the dynamics of phytoplankton community. During July and October, there is water column stratification; meanwhile in March, there is a well‐mixed water column. In addition, in May and July campaigns, hypoxia/anoxia conditions are detected at the bottom. The most abundant phytoplankton groups are Diatoms and Cryptophyceae. Diatoms and Cyanophyceae respond positively to temperature while Cryptophyceae, Prasinophyceae and Dinophyceae respond to high salinity and dissolved oxygen values. Furthermore, picoplankton is correlated inversely with nutrient concentrations.     

Phytoplankton development and ecological status during a cyanobacterial bloom in a tributary bay of the Three Gorges Reservoir, China

Reservoirs can provide suitable conditions for cyanobacterial bloom development, which may impact on water quality and biological communities. Weekly surveys in a cyanobacterial bloom process were carried out in the mainstream and Xiangxi Bay of the Three Gorges Reservoir (China), from June 6 to July 18 in 2008. By application of the phytoplankton functional group approach, the spatiotemporal pattern, impact factors, and the ecological status based on Q index (assemblage index) were analyzed. The depth of euphotic layer was apparently the key factor driving the phytoplankton functional group variations. Longitudinal patterns of phytoplankton distribution were detected during this bloom: in the beginning phase, groups D (mainly Stephanodiscus hantzschii) and B (Cyclotella stelligera) dominated in the mainstream of the Three Gorges Reservoir and the mouth area of Xiangxi Bay, group Y (Cryptomonas species) dominated in the upper area, while groups J (mainly Pediastrum duplex), F (mainly Sphaerocystis schroeteri) and G (Pandorina morum and Eudorina elegans) were important in other areas; in the mid phase, group M became absolutely dominant in the whole region; and in the ending phase, besides groups M and Y, groups X2 (Chroomonas acuta, Pyramimonas nanella, etc.) and Lo (Ceratium hirundinella) became more important in the lower and upper area respectively. Generally the ecological status was bad, temporally varied with the bloom process. No spatial difference of ecological status was found in the mainstream, while longitudinal patterns in Xiangxi Bay were detected for different phases: firstly a few sites had relatively better status than the others, then nearly all the sites were in the bad condition, and at last the status in the downstream was better than that in the upstream. The longitudinal patterns of ecological status were related to phytoplankton distribution, disturbed by jacking from the downstream and flood from the upstream of Xiangxi Bay.     

雷达遥感在环境保护工作中的应用

雷达遥感具有穿透力和全天候作业的优势,在环境保护领域中应用需求广泛。面对国家日益严峻的环保形势和最新发射的环境雷达卫星,急需系统介绍雷达遥感技术在环保领域中的应用。文章通过全面分析合成孔径雷达（SAR）在溢油、水华、土壤湿度、植被长势、生物量以及应急监测等环境保护中的应用,为已经发射的环境一号雷达卫星提供明确的应用目标,并为构建全天候、全天时的环境天地一体化监测体系提供重要的技术参考。     

Double‐layer P2P networks supporting semantic search and keeping scalability

In peer‐to‐peer (P2P) networks, with the aim to support semantic search and keep scalability at the same time, a novel double‐layer P2P protocol is proposed. Firstly, keywords representing resource characteristics are compressed into bloom filters and structured P2P layer is constructed. Secondly, through analyzing one's bloom filters, each node extracts its interest, which is represented by a characteristic vector V. After obtaining common interest among nodes through comparing their Vs, a small‐world model is constructed, and another unstructured P2P layer is obtained. Consequently, on the basis of the decentralized architecture, a double‐layer semantic search P2P protocol is structured. When objective resource is being located, its similarity to local interest is used to determine whether it should be located in unstructured P2P semantic layer or structured layer adaptively, which not only improves search efficiency but also supports semantic location more widely. Copyright © 2013 John Wiley & Sons, Ltd.     

Growth of carbon impurity density and adequate divertor wall temperature for fusion experimental reactors

Sudden increase of carbon impurity called carbon bloom has terminated the energy breakeven condition in the present large tokamak. In order to lengthen the burning plasma state in the next device, carbon bloom has to be well suppressed. The temporal evolution of carbon impurity density is analytically examined by using a simple one-point kinetic or zero-dimensional model including the effects of graphite erosions due to oxygen and ion, and gettering for oxygen due to boron or beryllium. The growth of carbon bloom due to radiation-enhanced sublimation is discussed based on the effective self-sputtering of carbon. Even when the self-sputtering yield is less than unity, carbon density is observed to continuously increase with the discharge time if the oxygen gettering action is not perfectly conducted. From the present analysis and data on the erosion of carbon materials, and the evaporation of gettering materials, it is suggested that the divertor wall temperature has to be kept less than approximately 900–1000°C to avoid the continuous growth of the carbon density.     

高碳钢大方坯连铸水冷工艺参数优化试验研究

通过对大量低倍试样的检验找出了高碳钢大方坯中间裂纹产生的原因.经一定的计算及经验制定出了五个方案,进行了小型及扩大试验.从内部晶体结构方面阐述了高碳钢大方坯产生中间裂纹的原因,提出了中间裂纹产生于结晶器,发展于二冷区的新分析思路.     

Eutrophication, phytoplankton dynamics and nutrient removal in two man-made urban lakes (Palácio de Cristal and Serralves), Porto, Portugal

Urban lakes are prone to eutrophication because of a number of factors, including a high water residence time (slow flushing rate), and high nutrient loads from artificial feeding of waterfowl and fish by visitors and from waterfowl faeces, falling leaves and nutrient run‐off from adjacent areas. This study focuses on the ecology of two similar‐sized urban lakes in Porto, Portugal, that exhibit some differing characteristics conducive to different trophic states and nutrient removal efficiencies. Although similar in many aspects, the two reservoirs developed quite diverse phytoplankton communities. The higher nitrogen load to Palácio de Cristal Lake could be the result of the higher concentration in its underground influent stream, while a less‐oxidized nitrogen form (ammonia) is higher in Serralves Lake. Nitrate concentrations are higher in Palácio de Cristal Lake than in Serralves as a result mainly of high nitrate loads (maximum values above 80 mg L⁻¹) in its influent stream. Interestingly, however, its nitrate removal efficiency is greater than for Serralves Lake. Cyanobacteria are the dominal phytoplankton In both lakes throughout the year. However, only one genus of this group (Pseudoanabaena mucicola) was the dominant phytoplankton in Palácio de Cristal Lake, while five Cyanobacteria species co‐dominated in Serralves lake. Regular monitoring of Cyanobacteria and their toxins in urban recreation lakes is advised.     

ECO-HYDRAULICS TECHNIQUES FOR CONTROLLING EUTROPHICATION OF SMALL SCENERY LAKES-A CASE STUDY OF LUDAO LAKE IN SHANGHAI

The Ludao Lake with an area of 0.86 km2 and 50% water surface ratio, was taken as an example to study the eco-hydraulics techniques for preventing lake eutrophication. Besides external water inflow and outflow, the term related to internal local flow circulation was added in the continuity equation of two-dimensional horizontal hydrodynamic model, and further the hydrodynamic model was calibrated by the scenario of no water exchange. The velocity of 0.2 m/s was suggested to be the critical velocity of controlling algal bloom. To achieve the critical velocity in the whole lake, three factors were analyzed, which are wind, artificial external inflow augmentation and internal local flow disturbance by pump circulation. It is found that the role of wind can be disregarded. For the eco-hydraulics technique of external lake water inflow augmentation, the water flowing route should be firstly optimized, further, the lake inflow has a critical value under specified water level due to the narrow inlets, so the whole lake is difficult to reach the critical velocity to prevent algal bloom, and a combination of external inflow augmentation and internal local flowing disturbance should be considered. Simulation results show that the combination of external water inflow augmentation and internal local flow disturbance requires less eco-flow to achieve the global critical velocity than the sole internal local flow disturbance, for the Ludao Lake, the former requires total eco-flow of 25 m3/s, which reduces by 50% than the latter requiring total eco-flow of 52 m3/s.