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Water Quality Monitoring of the Bezerra River (Cascavel, Brazil) Using SR-TXRF Technique
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作者 Phallcha Luízar Obregón Fernando Rodolfo Espinoza-Quinones Aparecido Nivaldo Módenes 《Journal of Chemistry and Chemical Engineering》 2014年第6期587-595,共9页
The present study aims to monitor and assess the water quality of the Bezerra River located in the Western Brazilian Parana state. For the monitoring of river waters, six samplings were established per month during on... The present study aims to monitor and assess the water quality of the Bezerra River located in the Western Brazilian Parana state. For the monitoring of river waters, six samplings were established per month during one year. As indicators of the water quality, physico-chemical parameters such as water temperature, pH, turbidity, dissolved oxygen and COD (chemical oxygen demand) were chosen, as well as trace and majority element concentrations. It is noteworthy that the mean annual values of conductivity, turbidity and COD have progressively increased along the river with maximum values after the Cascavel western sewage treatment plant. Only 13 elements were found in the six collection points, but the metallic elements Cr, Mn, Fe, Cu and Zn have shown concentrations above the maximum limits recommended by Brazilian environmental legislation, suggesting the presence of highly polluting anthropogenic sources. Correlation analyses were used to determine the spatio-variability of water quality variables. The six collection sites were grouped into two clusters, with the element composition in the first cluster (sites 1, 2 and 6) being due to strong anthropogenic activities. The study of the Bezerra River water quality could help to develop municipal environmental policies and help with the management of water conservation in the Bezerra River basin. 展开更多
关键词 River water pollution physico-chemical parameters SR-TXRF (synchrotron radiation total reflection X-ray fluorescence) technique element concentrations statistical analysis.
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Surface plasmon polaritons of symmetric and asymmetric metamaterial slabs
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作者 张惠芳 曹迪 +4 位作者 陶峰 杨希华 王燕 阎晓娜 白丽华 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第2期439-449,共11页
The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negativ... The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated. 展开更多
关键词 surface plasmon polaritons META-MATERIALS symmetric and asymmetric slabs attenuated total reflection technique
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A Study on Student Reflection in Asynchronous Online Text-stimulated Discussions 被引量:1
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作者 李青 翁克山 《Chinese Journal of Applied Linguistics》 2010年第6期109-126,128,共19页
为了了解学生在网络协作学习中如何进行知识构建和互动,本研究探讨了学生在基于课文内容的非即时在线讨论中如何进行反思。研究着重识别学生参与讨论过程中反思的成份和应用的反思技能。根据建构主义理论的相关学说,这些反思技能被划分... 为了了解学生在网络协作学习中如何进行知识构建和互动,本研究探讨了学生在基于课文内容的非即时在线讨论中如何进行反思。研究着重识别学生参与讨论过程中反思的成份和应用的反思技能。根据建构主义理论的相关学说,这些反思技能被划分为个体认知反思技能和交际互动反思技能两类。通过分析学生在三次基于课文内容的非即时讨论中的帖子,发现学生反思的成份包含个人已有知识经验、课文内容、课外内容以及其他同学的见解,同时总结出学生在讨论过程中应用了十五种反思技能。此外,该研究还分析了学生所应用的各种反思技能的质量高低及各种反思技能被应用的频率。以这十五种反思技能作为最基本的分析单元,就可分析非即时在线讨论课文内容过程中的互动模式以及知识构建的模式和效果。 展开更多
关键词 asynchronous online text-stimulated discussion interaction individual- cognitive reflection techniques social-interactive reflection techniques
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A technique of reconstructing field for measuring sound reflection coefficients at arbitrary angles of incidence
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作者 HE Yuanan, LI Rui, HE Zuoyong (Harbin Engineering University Harbin 150001) 《Chinese Journal of Acoustics》 2001年第4期310-318,共9页
An improved reconstructing field method for measuring sound reflection coefficient of a large impedance surface at arbitrary incident angles is proposed in this paper. In order to get the reflection coefficient by the... An improved reconstructing field method for measuring sound reflection coefficient of a large impedance surface at arbitrary incident angles is proposed in this paper. In order to get the reflection coefficient by the Spatial Transformation of Sound Fields (STSF), the complex pressure on two parallel planes near by the material surface or the reflection surface must be measured. By the acoustic intensity measurement, the phases of complex pressure on two parallel planes are given. The results of the numerical simulations are shown that the error due to the finite size of the measurement area, and it may be reduced by using a dipole sound source. 展开更多
关键词 A technique of reconstructing field for measuring sound reflection coefficients at arbitrary angles of incidence
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