Investigations of nitrogen removal pathways in a biological packed bed reactor using elementary mass balances

Nitrogen cycle involves a complex set of potential biochemical pathways with reactions catalyzed by different microorganisms. Elementary mass balances for COD, DO, NH4-N and alkalinity were conducted and stoichiometric relationships were investigated to explain possible pathways of the nitrogen removal mechanisms in a lab-scale submerged down flow biological packed bed (BPB) reactor. Four sets of experiments were performed by modifying the organic loading and C/N ratio in comparison with steady-state conditions. Approximately 90% of COD and NH4-N removal occurred in two upper sections occupying 1/5 of the reactor height. The elementary mass balances could not explain all the experimental results with respect to nitrogen removal and oxygen consumption by known mechanisms. The mass balance calculations, excluding the possibility of nitrification, were in general in accordance with the observations indicating no or minimal NO3-N production. The theoretical stoichiometric requirements for nitrification reaction were satisfied in 6 experiments and in another 8 experiments nitrification may have occurred, but stoichiometry was not satisfied. Using C/N ratio as the variable, only at C/N ratio = 10, the predictions confirmed the possibility of nitrification in the same 3 (out of 4) assays as observed in practice. The results of this study reveal that the nitrogen transformations occurring in the studied reactor are complex and cannot be explained by simple mechanisms of microbial assimilation and nitrificatio

Real-Time Scheduling of Sensor and Actuator Networks

Real-time scheduling issues in sensor and actuator networks (SANs) was investigated. The research studies the real-time issues related to the interplay between acquisition of data from sensors, its use in controller development, and optimal, real-time task scheduling based on available computing resources. Real-time task scheduling with the goal of achieving optimal system performance was the focus. Task schedulability with higher task rates and resource efficiency was investigated. Consideration of task execution times less than the worst case execution times results in achieving higher task frequencies. The problem of handling overruns using local (a task overrun reduces only that particular task frequency) and global (a task overrun initiates reduction of all task frequencies) approaches was investigated. A bisection method is proposed that has the potential to achieve higher task rates and resource efficiency. A number of examples are used to illustrate the ideas and methods.Computer Science Departmen

Modeling and computer simulation of zero speed splice unwinds

A computer program for conducting model simulations for zero speed splice unwinds is described in this paper. A typical unwind system consisting of the unwinding material roll, festoon, dancer, and pull rolls is considered. The developed computer model is general enough to be applicable to a variety of unwinds containing these components. The paper also provides a procedure for determining zero speed splicing parameters when the characteristics of the festoon and the splicer, such as number of carriage rollers, festoon capacity, clamp and dwell time, etc., are given; this method can be employed for the selection of splicing parameters, such as acceleration and deceleration profiles, splice diameter, spindle speed profiles, etc. The computer model can predict the transport behavior of webs through the unwinds; this was verified by comparing data from model simulations and experiments on a production unwind. The computer program can be used to evaluate different scenarios of unwind operation prior to actual implementation on production unwinds. Thus, providing a significant benefit in terms of operational efficiency as well as improved process capability

Comparison of control strategies for roll-to-roll printing presses

Flexible printed electronics is touted to be a significant part of the future of the roll-to-roll (R2R) printing industry. Electronic devices, such as RFID tags, low-cost displays and lighting devices, polymer solar cells, sensors, etc., can be manufactured on a flexible substrate using roll-to-roll machines. In recent years there has been a significant focus towards printing electronics on a flexible substrate using R2R printing methods. These studies have primarily dealt with the feasibility of printing electronic components such as thin metal lines, electrodes, capacitors, thin film transistors, etc., on the flexible substrate. In order to realize the goal of low cost printing of electronics on a flexible substrate using R2R techniques, the web handling aspects related to R2R printing have to be addressed adequately. This paper focuses on the web handling aspects related to R2R printing by analyzing the print registration process using mathematical models and by studying control schemes to improve print registration.Mechanical and Aerospace Engineerin

Recent advances in web longitudinal control

Stable web transport through processing machinery is critical in the web processing industry. Demands for improved performance under a wide variety of dynamic conditions and web materials are placing additional emphasis on developing new advanced control techniques. Further, technological advances in areas such as drive hardware, microprocessors, and sensors, are opening up new possibilities for implementing advanced control methods that are robust to a number of process and material variations and result in superior performance over existing industrial control methods.Mathematical models of fundamentals elements in a web process line are presented. A systematic procedure for computing the equilibrium inputs as well as reference velocities of all rollers based on the master speed reference is given. Recently developed robust control methods for web longitudinal control are described. Implementation of the controllers on two experimental platforms is given, and a sample of the experimental results is presented. Finally, some potential new directions and future research topics are discussed.Mechanical and Aerospace Engineerin

Bioenhancing effects of naringin on atorvastatin

Naringin (CAS no: 10236-47-2) is a flavonone glycoside obtained from Citrus paradisi (grapefruit), a natural bioenhancer and reported to enhance the bioavailability of drugs by inhibiting cytochrome P450 and P-glycoprotein (P-gp). The aim of the present study was to investigate the effect of naringin on antihyperlipidemic properties of atorvastatin (AST) in tyloxapol induced hyperlipidemic rats and the effects were supported with measurement of plasma concentrations of AST by HPLC method. Animals received AST along with naringin (15 and 30 mg/kg) shown higher percent reduction in both cholesterol and triglycerides levels, when compared to animals received AST alone at dose of 25 and 50 mg/kg and it was found that the higher percent reduction in cholesterol and triglycerides was proportional to increase in plasma concentration of AST. From the results it is evident that the co-administration of naringin along with AST increased the plasma concentration of AST. The findings of the present study confirmed that naringin could be used as bioenhancer. The co-administration of AST and the diet with naringin (grapefruit) to the patients may potentiate the therapeutic efficacy of AST