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The intermittent aeration strategy was applied to the sequencing batch biofilm reactor (SBBR) for the enhanced treatment of urban sewage. Ammonia oxidizing bacteria was cultivated by inoculation. After 25 days cultivation shortcut nitrification was successfully achieved and nitrite accumulation rate could be up to 93%. In the start-up phase of shortcut nitrification, intermittent aeration could increase production of nitrite and promote the enrichment of ammonia oxidizing bacteria. It was concluded that temperature could affect nitrite accumulation. When temperature is in 25~35°C, the nitrite accumulation rate could be up to 90%.

With more and more extensive use of copper oxide nanoparticles ( CuO ENPs), potential risks have emerged to draw public attention. While toxicity data is still in lack of CuO ENPs to maize as the main agricultural crops in soil-cultivated. This research have reported the phytotoxicity of CuO ENPs at 0, 500, 1000 mg/kg concentration to maize (Zea mays L.) during different aging times from 0 d to 90 d in soil. CuO ENPs at 500 mg/kg presented more toxicity to maize than at 1000 mg/kg while growth inhibition decreased with the aging time.

On basis of limit equilibrium analysis methods for theory of unsaturated soil mechanics, silt subgrade slope stability under the condition of rainfall infiltration is analyzed and the factors affecting the stability of subgrade slope are presented in this article, which provides theoretical basis and technical support for future subgrade construction.

The foundation settlement of soft soil highway engineering is too large, resulting in pavement wave-like because of differential settlement between the structure and adjacent soft soil foundation, which seriously impacts on traffic safety. Considering the soft soil foundation in the foundation treatment methods of CFG pile, sand bag well, powder spraying pile, we analyze differential settlement on the degree of influence structure internal force distribution, then provide the reference for the design and calculation.

The extensive application of nanoparticles will inevitably lead them to be released into the environment, which causes potential hazard to the ecosystem. This study was to provide the information of the toxicity of CuO ENPs to BY-2 cells in vitro. Tabacco BY-2 cells were exposed to 4 mg/L and 12 mg/L CuO ENPs. Cell viability was evaluated in 0 h, 2 h, 4 h, 8 h, 12 h, 16 h, 20 h and 24 h. The viability of BY-2 cells exposed to CuO ENPs gradually decreased with exposure time and the exposure concentration increasing. After 24 hours exposure to 12 mg/L CuO ENPs, plasmolysis occurred in cells. Some ENPs were absorbed on the cell wall, and only a small number of ENPs entered the cell. Membrane leakage turned up. This might be caused by lipid peroxides, destroying biological membranes.

A model based on level set function is proposed to predict gas shielded arc welding. The model describes not only the free surface tracking of molten drop and metal transfer in gas metal arc welding, but it simulates the phase change on substrate during heat transfer，which is based on porous media theory. The result of simulation shows that this model can describe the drop diameters, transfer frequency and the shape of solidification precisely.

Combining the study of college Students' happiness，this text establishes a set of campus planning and design evaluation system related to college students' happiness degree from the perspective of student's personal use. Also a practical example is evaluated.