Modelling of secondary clarifier using regression analysis and artificial neural networks.

Mathematical models for the surface area of secondary clarifier were developed for wastewater generated from a dairy industry and from domestic sources, by correlating the parameters namely, surface area per unit flow rate (A/Q), influent concentration (C(O)), underflow concentration (C(U)), recycling ratio (r) and Mean Cell Residence Time (theta C) using multiple regression analysis. There was found a good correlation between the measured data and the model results with regression coefficients of 0.9. Thickener area requirement of combined wastewater was comparehat obtained for dairy wastewater. Thickener area was found to decrease with increase in Mean Cell Residence Time and the area required for treating the combined wastewater was less, when compared with the requirement for dairy wastewater treatment. Neural network was trained with experimental data to 'acquire' knowledge about it. The Back Propagation Network technique was used in which the error was back propagated through the network. The results evolved from the neural network training were compared with the results of regression model and experimental data. Greater deviation was observed between the observed and predicted values of A/Q at high underflow concentrations, indicating that the limiting solids flux was reached. The output from Neural Network approach had greater consistency with the experimental data than the output from conventional regression analysis. Hence, Artificial Neural Network technique is highly adaptive and efficient in investigating input - output relationships.

Single-plate Molteno implants in complicated glaucomas: results, survival rates, and complications.

Sixty-two single-plate single-stage Molteno implantations for complicated glaucomas were performed between March 1991 and November 1992. The charts of all these patients were reviewed to determine the intraocular pressure (IOP) control success rate (< 21 mm Hg with or without medications), visual success rate (retention or improvement of visual acuity from preoperative level) and the rate of complications encountered. A Kaplan-Meier life-table (survival) analysis was also performed. IOP control was obtained in 74.2% of cases. Mean postoperative IOP was 16.97 +/- 8.07 mm Hg (Mean +/- SD). Visual success was obtained in 51.6% of the eyes. Eyes with aphakia/pseudophakic glaucomas showed the best response with 80% of them achieving IOP control and 60% achieving visual success. The survival plot for IOP control revealed 75.81% and 74.19% success rates at 48 and 72 weeks, respectively. Complications encountered were either due to the early postoperative hypotony or were tube-related. These results were gratifying considering the severity of the glaucoma in these cases and they reaffirm the usefulness of the Molteno implant in the management of difficult glaucomas.