| 1 | Physicochemical water quality parameters in typical rice-crayfish integrated systems(RCIS)in China显示文摘To determine the variation of water quality in rice-crayfish(Procambarus clarkii)integrated systems(RCIS)in China,eleven water quality parameters were measured monthly in a typical RCIS located in Qianjiang City(Hubei Province)from July 2014 to June 2015,the parameters were analyzed with principal component analysis(PCA)and compared between the trenches and rice areas during the rice fallow period(Nov-May).The trench and rice area comprehensive results showed that pH(7.48-8.68),NH_(4)^(+)-N(0.2-1.09 mg/L),NO_(2)^(-)-N(<0.052 mg/L)and conductivity(435-951μS/cm)were within the suitable ranges for P.clarkii and that turbidity(TU)was high during the crayfish harvesting and rice planting season.Annual averages of total nitrogen(TN),total phosphorus(TP),permanganate index(CODMn),and chlorophyll a(Chl.a)content were<2(except in Nov-Dec),0.25,10 mg/L,and 50 mg/m^(3)(especially in Nov-May,<10 mg/m^(3)),respectively.Dissolved oxygen(DO)was below 4 mg/L in Mar-Sep,with a minimum of~1 mg/L,and much higher in Oct-Feb.The maximum and minimum monthly average water temperature(WT)were 31.4°C in July and 5.7°C in December,while the maximum and minimum instantaneous WT were 39.7°C and 2.5°C,respectively.PCA analysis showed that the first three axes,which were mainly correlated with DO,WT and nutrient level,described most information of the parameters,and parameters showed seasonal changes.Some differences were observed in water parameters between the trenches and rice areas,i.e.,trenches generally had higher TU,WT and DO,and lower TN,TP and CODMn,although no significant differences were found in some months and some parameters.The study revealed relatively low water nutrient level,probable extreme WT and DO level in some seasons,and certain differences between the trenches and rice areas in typical CRIS in China.Accordingly,some measures should be taken to improve the negative parameters:1)enhance the water fertility;2)increase DO,especially in Mar-Sep;3)increase the trench and water depth to avoid extreme WT.And water quality management should be addressed in both trenches and rice areas. | Jixin Yu Yan Ren Tao Xu Wei Li Mantang Xiong Tanglin Zhang Zhongjie Li Jiashou Liu | 2018 | International Journal of Agricultural and Biological Engineering2018，11，3： | 6 |
| 2 | Optimal design of velocity sensor for open channel flow using CFD显示文摘In this study,computational fluid dynamics(CFD)was used to design the geometry of a new velocity sensor for measuring open channel flows.This sensor determined velocity by observing the travel of dye carried in the flow.Evaluation of this design required the development of fluid dynamics models to determine potential errors in fluid velocity measurement due to velocity changes caused by intrusion of the sensor in the fluid.It also required an analysis technique to determine the expected sensor response to the flow fields that resulted from the CFD modeling.These models were then used to improve the geometry of the sensor to minimize the measurement error.Starting with a simple design for the sensor geometry,the CFD analysis modeled the open channel flow around the sensor as turbulent using both the k-ωand k-εReynolds Averaged Navier-Stokes(RANS)turbulence models.The model predicted that the original sensor design would underestimate the free-stream velocities of open channels by 7.9%to 2.0%across a range from 0.1 m/s to 5.0 m/s.After using CFD to improve the sensor design,the velocity measurement error was limited to less than 4%across the same velocity range. | Joseph Scot Dvorak Naiqian Zhang | 2017 | International Journal of Agricultural and Biological Engineering2017，10，3： | 0 |
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