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最低价评标法若干问题探析 总被引:1,自引:0,他引:1
赵夫国 《宁波大学学报(理工版)》2002,15(2):31-34
从我国建设工程招投标评标方法入手,论述了最低价评标法的优缺点,分析了应用最低价评标法应把握几个问题,最后提出了实际最低价评标法的几项保障措施。 相似文献
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Synthesis and Modification of Zn‐doped TiO2 Nanoparticles for the Photocatalytic Degradation of Tetracycline
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Shuo Pang Ji‐guo Huang Yun Su Bo Geng Su‐yuan Lei Yu‐ting Huang Cong Lyu Xing‐juan Liu 《Photochemistry and photobiology》2016,92(5):651-657
The synthesis of Zn‐doped TiO2 nanoparticles by solgel method was investigated in this study, as well as its modification by H2O2. The catalyst was characterized by transmission electron microscopy, X‐ray diffraction, Brunauer–Emmett–Teller, UV–visible reflectance spectra and X‐ray photoelectron spectroscopy (XPS). The results indicated that doping Zn into TiO2 nanoparticles could inhibit the transformation from anatase phase to rutile phase. Zn existed as the second valence oxidation state in the Zn‐doped TiO2. Zn‐doped TiO2 that was synthesized by 5% Zn doping at 450°C exhibited the best photocatalytic activity. Then, the H2O2 modification further enhanced the photocatalytic activity. Zn doping and H2O2 modifying narrowed the band gap and efficiently increased the optical absorption in visible region. The optimal degradation rate of tetracycline by Zn‐doped TiO2 and H2O2 modified Zn‐doped TiO2 was 85.27% and 88.14%. Peroxide groups were detected in XPS analysis of H2O2 modified Zn‐doped TiO2, favoring the adsorption of visible light. Furthermore, Zn‐doped TiO2 modified by H2O2 had relatively good reusability, exhibiting a potential practical application for tetracycline's photocatalytic degradation. 相似文献
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以花粉可育率和自然结实率为指标,对红莲型细胞质雄性不育系丛广41 A 与其恢复系配制的 F1 、 F2 、 B C1 和 B C2 等世代的育性表现进行了调查,结果表明,红莲型细胞质雄性不育系丛广41 A 属配子体不育,其不育性受一对隐性核主基因和不育细胞质共同控制,其核不育基因与珍汕 97 A 不等位 其恢复性受显性单基因控制,密阳 23 有一对强恢复基因,珍汕 97 有一对弱恢复基因 相似文献
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基于新的势能面,运用半刚性振动转子靶(SVRT)模型和含时波包法对Cl+CH4→HCl+CH3反应体系进行了计算,给出了反应过程中体系的振动、转动及空间立体效应对该反应的反应几率和反应阈能的影响,并计算了基态的总散射截面和热速率常数. 相似文献
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Kouakou TH Kouadio YJ Kouamé P Waffo-Téguo P Décendit A Mérillon JM 《Applied biochemistry and biotechnology》2009,158(2):285-301
Polyphenol oxidases (PPOs) were isolated from cell suspensions of two cultivars of cotton (Gossypium hirsutum L.), and their biochemical characteristics were studied. PPO from Coker 312, an embryogenic cultivar, showed a highest affinity
to catechol 20 mM, and PPO from R405-2000, a nonembryogenic cultivar, showed a highest affinity to 4-methylcatechol 20 mM.
The optimal pH for PPO activity was 7.0 and 6.0 for Coker 312 and R405-2000, respectively. The enzyme had an optimal temperature
of 25 °C and was relatively stable at 20–30 °C. Reducing sodium metabisulfite, ascorbic acid, dithiothreitol, SnCl2, and FeCl3 markedly inhibited PPO activity, whereas its activity was highly enhanced by Mg2+, Ca2+, and Mn2+ and was moderately inhibited by Ba2+, Cu2+, and Zn2+. The analysis revealed a single band on the sodium dodecyl sulfate polyacrylamide gel electrophoresis which corresponded
to a molecular weight of 55 kDa for Coker 312 and 42 kDa for R405-2000. 相似文献