The relationship between the automatic control method and the stability of the open canal is studied by means of numerical simulation of unsteady flow in an open canal under different methods of control. It is found the Proportional-Proportional plus Reset （P＋PR） control is more reliable than the Linear Quadratic Regulator （LQR） control. Moreover, for the P＋PR control, the hydraulic response of the constant volume method of operation is better than that of the constant downstream depth method in the type of centrally controlled canal. Therefore, an appropriate flow change rate should be chosen instead of shortening the pool length to reach an acceptable drawdown rate. For the canal with a bottom width of 40 m, side slope of 3, Manning n of 0.015, bottom slope of 0.000 04, and design flow of 600 m3/s, the pool length of more than 30 km can provide acceptable drawdown rates of 0.2 m/h when a proper flow change rate is chosen.
定量化研究重金属镉在碱性土壤中的迁移对我国北方水土资源环境的保护具有重要意义。本文以保守性溶质Cl-作为参照,以饱和土柱中开展的镉(Cd2+)在3种土壤、2种输入浓度条件下的室内易混合置换实验为模拟对象,运用连续时间随机游动(Continuous Time Random Walk,CTRW)理论,模拟Cl-和Cd2+在几种特定实验条件下的运移动态。模拟值与实测值的对比显示,无论是保守性溶质Cl-还是重金属Cd2+,CTRW理论都能够较好地拟合它们在不同实验条件下的穿透行为,较完整地刻画出它们在供试土壤中出流液浓度的动态过程。相对于保守性示踪剂仅受到物理非平衡条件的影响,同一土柱中的重金属镉的运移同时还受到化学非平衡条件的影响,因而导致了镉与示踪剂所对应的CTRW参数的差异。本文对CTRW理论在重金属运移行为模拟中的应用,既是对该理论模拟重金属镉在水土环境中迁移的有效性的评价,同时也在一定程度上为深化对CTRW中参数物理意义的理解,特别是为进一步加深对这些参数与非平衡条件之间的关系的理解提供了重要的参考依据。
As the bioelectrochemical system, the microbial fuel cell （MFC） and the microbial electrolysis cell （MEC） were developed to selectively recover Cu^2＋ and Ni^2＋ ions from wastewater. The wastewater was treated in the cathode chambers of the system, in which Cu^2＋ and Ni^2＋ ions were removed by using the MFC and the MEC, respectively. At an initial Cu^2＋ concentration of 500 mg· L^-1, removal efficiencies of Cu^2＋ increased from 97.0%±1.8% to 99.0%±0.3% with the initial Ni^2＋ concentrations from 250 to 1000 mg· L^-1, and maximum power densities increased from 3.1±0.5 to 5.4±0.6W.m-3. The Ni^2＋ removal mass in the MEC increased from 6.84-0.2 to 20.54-1.5 mg with the increase of Ni^2＋ concentrations. At an initial Ni^2＋ concentration of 500 mg· L^-1, Cu^2＋ removal etticiencies decreased from 99.1%±0.3% to 74.2%±3.8% with the initial Cu^2＋ concentrations from 250 to 1000 mg -L1, and maximum power densities increased from 3.0±0.1 to 6.3±1.2W.m^-3. Subsequently, the Ni^2＋ removal efficiencies decreased from 96.9%-4-3.1% to 73.3%4-5.4%. The results clearly demonstrated the feasibility of selective recovery of Cu2~ and Ni2~ from the wastewater using the bioelectrochemical system.
Haiping LUO Bangyu QIN Guangli LIU Renduo ZHANG Yabo TANG Yanping HOU
