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471.
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桥梁伸缩装置(以下简称伸缩缝)使用环境恶劣、受荷形式复杂,易出现多种病害。伸缩缝病害会造成桥梁耐久性降低,车致桥梁动力响应加重等不利现象。因此,伸缩缝病害机理及其处置方法和考虑伸缩缝参数影响的车-桥耦合动力响应规律研究受到了广泛关注。本文综述了桥梁伸缩缝力学性能,常见病害及其影响,病害机理及其处置方法等的发展现状;重点讨论了考虑伸缩缝参数及其变化影响的桥梁动力响应的研究进展及存在的问题;展望了未来桥梁伸缩缝研究中有待解决的关键问题。 相似文献
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水相中CCl4和CHCl3的紫外光解机理 总被引:2,自引:0,他引:2
利用瞬态吸收光谱技术研究水体污染物CCl4和CHCl3在紫外光照条件下的转化和归宿,表明在248nm激光作用下,CCl4解离为CCl3和Cl自由基;CHCl3在此条件下不解离,但加入少量的苯后即发生明显解离,产生CHCl2和Cl自由基.在有氧条件下,光解产生的CCl3和CHCl2自由基均与O2反应分别生成CCl3O2和CHCl2O2;在无氧条件下,CCl3和CHCl2则发生偶合反应分别生成C2Cl6和C2H2Cl4.本研究还得出了一些微观速率常数. 相似文献
475.
Yang Xiuping Jia Yunting Zhang Dacheng Zhang Xuemei Zhang Hua Hou Yujun 《Environmental science and pollution research international》2020,27(32):40020-40040
Environmental Science and Pollution Research - Given the relatively harsh natural environment in semi-arid valley areas, the attraction and radiation functions of semi-arid valley cities have... 相似文献
476.
Cui Yan Zhu Wei Wu Silin Liu Jiming Hou Hao Lin Naixi 《Environmental science and pollution research international》2021,28(14):17331-17342
Environmental Science and Pollution Research - Dredged mud is a kind of construction material that can be reused as waste. It needs to be dehydrated before it is used. At present, plate and frame... 相似文献
477.
Hao Zhang Yubin Zhang Zhiguang Hou Xian Wu Henan Gao Fengjie Sun 《Journal of environmental science and health. Part. B》2013,48(2):79-86
By enrichment culturing of soil contaminated with metribuzin, a highly efficient metribuzin degrading bacterium, Bacillus sp. N1, was isolated. This strain grows using metribuzin at 5.0% (v/v) as the sole nitrogen source in a liquid medium. Optimal metribuzin degradation occurred at a temperature of 30ºC and at pH 7.0. With an initial concentration of 20 mg L?1, the degradation rate was 73.5% in 120 h. If the initial concentrations were higher than 50 mg L?1, the biodegradation rates decreased as the metribuzin concentrations increased. When the concentration was 100 mg L?1, the degradation rate was only 45%. Degradation followed the pesticide degradation kinetic equation at initial concentrations between 5 mg L?1 and 50 mg L?1. When the metribuzin contaminated soil was mixed with strain N1 (with the concentration of metribuzin being 20 mg L?1 and the inoculation rate of 1011 g?1 dry soil), the degradation rate of the metribuzin was 66.4% in 30 days, while the degradation rate of metribuzin was only 19.4% in the control soil without the strain N1. These results indicate that the strain N1 can significantly increase the degradation rate of metribuzin in contaminated soil. 相似文献
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Abstract A pot experiment was conducted to investigate the influence of citric and oxalic acids effect on Pb and Zn uptake by corn and winter wheat. The experiment was employed with citric acid (CA) applied at 3 rates (0, 1.5 and 3.0 mmol kg?1 soil), oxalic acid (OA) at 3 rates (0, 1.5 and 3.0mmol kg?1 soil) and citric acid combined with oxalic acid (1.5 mmol citric acid combined with 1.5 mmol oxalic acid kg?1). Two types of soil were chose in the experiment. One was collected from the agricultural soil near a battery-recycling factory in Anhui province, China (site A) and the other was collected from a Pb-Zn mine residues in Hunan province, China (site B). The results showed that soil pH varied with the different treatment of citric and oxalic acids. However, there were no differences in all the treatments. 3.0mmol CA kg?1 soil addition significantly increased the concentrations of the CaCl2-extractable Pb and Zn and other treatments have no significantly increased. The highest shoot concentrations of Pb and Zn in both species occurred in application of 3.0 mmol CA/kg?1 soil and shoot concentrations of Pb and Zn in both species were significantly higher than the controls in this treatment. Shoot yields declined with application of citric and oxalic acids, indicating that the plants were sensitive to the toxicity of the metals or the amendments. The highest Pb uptake values by maize and wheat werell2.3 and 77.2 μg pot1 in soil of site A, and occurred with the control and 3.0 mmol CA/kg?1 soil respectively. 相似文献
480.