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In order to discuss the effect of the release of nitrogen and phosphorus from root exfoliation of water hyacinth (Eichhornia crassipes) on water quality during the course of eutrophic water purification, water hyacinth was cultivated in confined fence facilities in the Caohai of Dianchi Lake. The plant and root exfoliation were collected every 30 days from May to November in the year of 2013, and fresh and dry weight as well as nitrogen and phosphorus contents were determined. The results showed there was no significant difference (P>0.05) between May-Sep (rapid growth period) and Oct-Nov (gradual withering period) on the contents of nitrogen and phosphorus in dry matter of water hyacinth, while the growth rate of water hyacinth in rapid growth period was significantly (P

In order to compare two different floating aquatic plants about the nitrogen removal effect of eutrophic water in Lake Dianchi Caohai, Eichhornia crassipes and Pistia stratiotes were employed to microcosm experiments. Results showed that Eichhornia crassipes and Pistia stratiotes had no obvious difference on the ability of nitrogen enrichment and the total nitrogen removal rate. Under the water total nitrogen (TN), dissolved total nitrogen(DTN), nitrate(NO3--N), ammonium(NH4+-N)initial concentration of 8.40, 7.20, 4.12, 2.59 mg·L-1, Eichhornia crassipes and Pistia crassipes seedlings were 1 kg, the average total nitrogen(TN), dissolved total nitrogen(DTN), nitrate(NO3--N), ammonium(NH4+-N)removal rate of Eichhornia crassipes test group were 74.24%, 76.81%, 87.62%, 80.30%respectively; The average total nitrogen(TN), dissolved total nitrogen(DTN), nitrate(NO3--N), ammonium(NH4+-N)removal rate of Pistiacrassipes test group were 70.10%, 78.89%, 94.77%, 87.64% respectively. The average assimilation away from total nitrogen in water nitrogen loss rate of Eichhornia crassipes and Pistia crassipes test group were 89.39% and 82.33% respectively. The average nitrogen content in the sediment of nitrogen in the water loss rate of Eichhornia crassipes, Pistia crassipes and control test group were 6.94%, 11.64% and 83.51% respectively. Eichhornia crassipes and Pistia crassipes could not only effectively inhibit the formation of sediment, but also could significantly decrease the DO and pH of the water. Although Eichhornia crassipes and Pistia stratiotes can significantly reduce the total nitrogen of water, considering the Pistia stratiotes plant is brittle, so large-scale Eichhornia crassipes planting is a feasible way to control eutrophication of lakes.

A single-machine scheduling model is proposed for minimizing the expected total cost consisting of flowtime cost and asymmetric penalty cost of earliness-tardiness subject to machine breakdowns. All jobs have a common due date and an identical piecewise linear cost function. Since it is difficult to calculate the exact value of expected total cost, an approximate function of expected total cost is introduced to simplify the scheduling model. Dominance conditions necessary for an optimal schedule are derived for this scheduling problem. Efficient methods exploiting these conditions are proposed for obtaining an optimal schedule minimizing the modified expected total cost. Numerical examples are demonstrated to show the effectiveness of the proposed methods.