Neural network prediction of thermophilic (65 degrees C) sulfidogenic fluidized-red reactor performance for the treatment of metal-containing wastewater

The performance of a fluidized-bed reactor (FBR) based sulfate reducing bioprocess was predicted using artificial neural network (ANN). The FBR was operated at high (65 degrees C) temperature and it was fed with iron (40-90 mg/ L) and sulfate (1,000-1,500 mg/L) containing acidic (pH = 3.5-6) synthetic wastewater. Ethanol was supplemented as carbon and electron source for sulfate reducing bacteria (SRB). The wastewater pH of 4.3-4.4 was neutralized by the alkalinity produced in acetate oxidation and the average effluent pH was 7.8 +/- 0.8. The oxidation of acetate is the rate-limiting step in the sulfidogenic ethanol oxidation by thermophilic SRB, which resulted in acetate accumulation. Sulfate reduction and acetate oxidation rates showed variation depending on the operational conditions with the maximum rates of 1 g/L/d (0.2 g/g volatile solids (VS)/d) and 0.3 g/L/d (0:06 g/g VS/d), respectively. This study presents an ANN model predicting the performance of the reactor and determining the optimal architecture of this model; such as best back-propagation (BP) algorithm and neuron numbers. The Levenberg-Marquardt algorithm was selected as the best of 12 BP algorithms and optimal neuron number was determined as 20. The developed ANN model predicted acetate (R=0.91), sulfate (R=0.95), sulfide (R=0.97), and alkalinity (R=0.94) in the FBR effluent. Hence, the ANN based model can be used to predict the FBR performance, to control the operational conditions for improved process performance

An Assessment of Hierarchical Linear Modeling in International Business, Management, and Marketing

International marketing research, in most cases, involves at least two levels (e.g., firms within countries) that make the hierarchical linear modeling (HLM) a suitable data analysis technique. Due to its robustness, the use of HLM in the international business (IB) research has increased substantially over the last decade. However there is still a lack of standardization in the fundamental issues that hinders the wide spread use of HLM. This study provides unified approach to HLM use in IB research by providing standards for appropriate use of HLM. To achieve this goal, a detailed analysis of the method\u27s use in 42 IB studies is provided and these studies are compared with 104 non-international studies to determine where IB research stands in terms of HLM use. Finally this study focuses on the good HLM practices and offers suggestions designed to maximize the effective use of HLM and potential in international business studies