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Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions. 相似文献
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超强吸水树脂的吸水性能研究 总被引:15,自引:0,他引:15
对自制的超强吸水树脂的吸收性能进行了研究,分别考察了吸水树脂的粒径,溶液的pH值,几种离子如Na^ ,K^ ,Ca^2 ,Mg^2 等的水溶液对吸水树脂吸收性能的影响。实验结果表明,在pH为6-8,树脂粒径为100mesh-120mesh时,树脂的吸水性能最好,各种离子对吸水树脂吸收性能的影响大小顺序为:Na^ <K^ <Mg^2 <Ca^2 。 相似文献
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在ATM网里业务阻塞控制是一个十分重要的问题,本文对一种缓冲漏桶业务阻塞控制算法在突发性业务输入情况下的性能进行了计算机模拟分析,模拟结构表明缓冲漏桶算法是一种适合于突发性业务的阻塞控制算法,文章在模拟结果的基础上给出了缓冲漏桶算法中参量选择的算法。 相似文献
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Weihua Jiang Zinsmeyer K. Less M. Schoenbach K.H. Kristiansen M. 《Electron Devices, IEEE Transactions on》1994,41(4):582-586
Results of electron-beam controlled switching experiments with switch samples of quartz crystal and polycrystalline zinc selenide (ZnSe) are presented. For switch samples of both materials, drastic reductions of the switch resistance were induced by the electron beam. The quartz sample showed very fast temporal response (less than 1 ns) with potential applicability for current control. The ZnSe samples, on the other hand, showed longer current transients (on the order of 10 ns) with exponential development of the switch resistance after the electron beam pulse 相似文献
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Shaofeng Wang Yuan Hu Zhihua Lin Zhou Gui Zhengzhou Wang Zuyao Chen Weicheng Fan 《Polymer International》2003,52(6):1045-1049
Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry 相似文献