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Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric... 相似文献
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创新研究生资助体系 完善研究生培养机制 总被引：3，自引：0，他引：3
一、目前研究生资助体系存在的问题 目前,我国的研究生人数已经超过百万,在数量上已经位居世界第一.我国教育事业在"十一五"期间的一个重要目标就是要提高高等教育的质量,不能仅仅以数量取胜,关键是在培养质量上.现在的数量是上去了,但是,对高等教育的投入以及相应的人才政策、管理措施还不处于优势,人才培养的质量与国外相比还有很大的差距.从1978年改革开放至今已经30年了,我国的研究生培养机制还是采用上个世纪七八十年代制订的那一套旧的资助体制,它已经不能适应现代高等教育的发展了. 相似文献
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一、目前研究生资助体系存在的问题
目前,我国的研究生人数已经超过百万,在数量上已经位居世界第一。我国教育事业在“十一五”期间的一个重要目标就是要提高高等教育的质量,不能仅仅以数量取胜,关键是在培养质量上。现在的数量是上去了,但是,对高等教育的投入以及相应的人才政策、管理措施还不处于优势,人才培养的质量与国外相比还有很大的差距。从1978年改革开放至今已经30年了,我国的研究生培养机制还是采用上个世纪七八十年代制订的那一套旧的资助体制,它已经不能适应现代高等教育的发展了。 相似文献
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Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric analysis was conducted to simulate variations in soil dry density, temperature, pH and standing time. The results show that the method used in this paper is simple and effective. The diffusion coefficient of Cr(Ⅵ) in Dalian red clay varies from 1.50×10-7 cm2/s to 2.08×10-7 cm2/s. After 1 000 d diffusion, the concentration of the source solution drops down to 1.27 mg/L from 62.5 mg/L, and the diffusion distance is only 3.5 cm. Under the assumption that diffusion coefficient is constant, the diffusion effect becomes more obvious with lower density, lower temperature, higher pH value, and much more time. 相似文献
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