Real Time Control of pH in Fed‐Batch Process

Abstract

The objective of this work is to implement the linear, non linear model based and linear cascade controllers to control pH in a fed batch neutralisation process in real time and compare the performance with the simulation results. The control objective here is to make the process output pH to follow the given reference trajectory. This work aims at bringing out the best features of model‐based control and linear cascade control, when applied to highly non‐linear systems like pH‐controlled fed‐batch processes. For these processes, control of pH by a conventional Proportional Integral Derivative controller fails to provide satisfactory performance because of the extreme non‐linearity in the pH dynamics. Typical problems in control, e.g., uncertainty in model parameters, are addressed in this work. These controllers are implemented in real time using a lab scale setup and compared with the simulation. The results show the superior performance of the non linear model‐based and linear cascade controller over that of the conventional Proportional Integral controller.     

Model Based Controller and Linear Cascade Controller Applied to Fed Batch pH Process

Abstract

The present study aims at bringing out the best features of model‐based control, linear cascade control when applied to highly non‐linear systems like pH‐controlled fed‐batch processes. For these processes, control of pH by conventional Proportional‐Integral‐Derivative controller fails to provide satisfactory performance, because of the extreme non‐linearity in the pH dynamics. In the present study, for a fed‐batch neutralization process, a non‐linear control law has been derived for the model‐based Proportional Integral controller. Typical problems in process control like sampling, delay and perturbations in model parameters are addressed in this study using model‐based control. The simulation results show the superior performance and robustness of the model‐based controller and linear cascade controller over that of the conventional Proportional Integral controller.     

Wavelet analysis for estimation of mean-curve of impulse waveformssuperimposed by noise, oscillations and overshoot

This paper describes a novel approach to estimate the mean-curve of impulse voltage waveforms that are recorded during impulse tests. These waveforms in practice are superposed by noise, oscillations, and overshoot. The approach is based on multiresolution signal decomposition (a kind of wavelet transform) and has many advantages over existing methods, since it does not assume any model for estimating the mean-curve, is interactive in nature, suitable for full and chopped impulses, does not introduce distortions due to its application, is easy to implement and does not call for changes to existing standards. Results presented show its applicability     

Synthesis and characterization of polyaniline derivative and silver nanoparticle composites

BACKGROUND: There has been a recent surge of interest in the synthesis and applications of electroactive polymers with incorporated metal nanoparticles. These hybrid systems are expected to display synergistic properties between the conjugated polymers and the metal nanoparticles, making them potential candidates for applications in sensors and electronic devices. RESULTS: Composites of polyaniline derivatives—polyaniline, poly(2,5‐dimethoxyaniline) and poly(aniline‐2,5‐dimethoxyaniline)—and silver nanoparticles were prepared through simultaneous polymerization of aniline derivative and reduction of AgNO₃ in the presence of poly(styrene sulfonic acid) (PSS). We used AgNO₃ as one of the initial components (1) to form the silver nanoparticles and (2) as an oxidizing agent for initiation of the polymerization reaction. UV‐visible spectra of the synthesized nanocomposites reveal the synchronized formation of silver nanoparticles and polymer matrix. The morphology of the silver nanoparticles and degree of their dispersion in the nanocomposites were characterized by transmission electron microscopy. Thermogravimetric analysis and differential scanning calorimetry results indicate an enhancement of the thermal stability of the nanocomposites compared to the pure polymers. The electrical conductivity of the nanocomposites is in the range 10^?4 to 10^?2 S cm^?1. CONCLUSION: A single‐step process for the synthesis of silver nanoparticle–polyaniline derivative nanocomposites doped with PSS has been demonstrated. The approach in which silver nanoparticles are formed simultaneously during the polymerization process results in a good dispersion of the nanoparticles in the conductive polymer matrix. Copyright © 2008 Society of Chemical Industry     

Methodology for the evaluation of scientific journals: Aggregated Citations of Cited Articles

The criteria for the evaluation of scientific journals have changed from characteristics of its contents to citations of articles. Among many problems associated with citation-based evaluation methods are that it is applicable only to a limited number of journals, preferential selection of citable documents, differential values to citations, time duration for assessment, etc. The proposed index, Aggregated Citations of Cited Articles (ACCA), is calculated based on citations data, derived from only of cited articles, and therefore can be validated from standard database. While giving more importance to citations, the number of cited articles published in a journal also has some influence in the new index. The calculated values are consistent with time and can be used to back-track the status of a journal in its past and for continued evaluation. The new Index ensures neutrality, qualitative and quantitative hierarchy and consistency in the estimation of journal ranking.     

Vanillin rich fraction regulates LDLR and HMGCR gene expression in HepG2 cells

Vanillin and its analogs have been exploited for their various health benefits. This work aimed to investigate the antioxidant properties and regulatory effects of vanillin rich fraction (VRF) extracted from vanilla pods using the supercritical fluid extraction (SFE) and commercial vanillin on low density lipoprotein receptor (LDLR) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) gene expression in HepG2 cells. The vanillin content in the VRF was 2.6% (w/w) obtained at a temperature of 80 °C and a pressure of 600 bar. The VRF exhibited better antioxidant activity compared to the vanillin in DPPH and BCB tests. LDLR mRNA level was increased significantly by 2, 3 and 1.3 fold in the VRF treated cells at 100, 200 and vanillin treated cells at 100, respectively, compared with untreated cells. On the other hand, the HMGCR mRNA level was decreased significantly by 14, 58 and 13% respectively, in the VRF treated cells at 100, 200 and V treated cells at 100, respectively, compared with untreated cells. The VRF showed potential antioxidant activity and regulated genes involved in cholesterol metabolism including LDLR and HMGCR in dose-dependent manner.     

Structure-function validation of high lysine analogs of {alpha}-hordothionin designed by protein modeling

Cereal grains and legume seeds, which are key protien sourcesfor the vegetarian diet, are generally deficient in essentialamino acids. Maize, in particular, is deficient in lysine. Theinherent lack of lysine-rich protiens in maize has necessitatedthe search for heterologous protiens enriched in this aminoacid, the isolation of the corresponding gene and its ultimateintroduction into maize through plant transformation techniques.However, a rate-limiting step to this strategy has been theavailability of plant-derived lysine-rich protiens. An appealingsolution to the problem is to artificially increase the lysinecontent of a given protein by mutating appropriate residuesto lysine. Here, we expound this strategy, starting with theprotein hordothionin that is derived from barley seeds andconsists of five lysine residues in a total of 45 amino acids(11 % lysine). To facilitate rational substitutions, the 3-Dstructure of the protein has been determined by homology modelingwith crambin. based on this model, we have identified surfaceresidues amenable to substitution with lysine. Furthermore,the acceptability of the mutations has been validated throughthe syntheses and characterization of the derivatives. To thisend, our approach has permitted the creation of a modified -hordothionin protein that has a lysine content of 27 % andretains the antifungal activity of the wild-type protein.