Rama Rao Karri

Bio: Rama Rao Karri is an academic researcher from Institut Teknologi Brunei. The author has contributed to research in topics: Adsorption & Medicine. The author has an hindex of 24, co-authored 80 publications receiving 1590 citations. Previous affiliations of Rama Rao Karri include National University of Singapore.

Optimal isotherm parameters for phenol adsorption from aqueous solutions onto coconut shell based activated carbon: Error analysis of linear and non-linear methods

Abstract: Removal of phenolic pollutants from wastewaters has become mandatory due to stringent environmental regulations and adverse effects on aquatic marine environment. Adsorption process which is most effective process to remove pollutants, hinders its applications in diverse field due to high cost of adsorbents. In this study, a low cost and easily available agricultural waste of coconut shells based activated carbon were utilized as adsorbent to study its viability and efficiency for phenol removal from wastewater. The efficacy of the phenol removal by adsorption process in a batch reactor is evaluated with respect to contact time for effective adsorption and influence of initial phenol concentration on percentage phenol removal. The experimental adsorption data were examined with conventional isotherms models to describe the equilibrium characteristics of adsorption of phenol. The vigorousity and non-linearity inherent in the isotherm models were validated using various traditional linear and non-linear estimation methods namely gradient method, non-linear least square method and hybrid evolutionary optimization. A novel inverse modeling technique based on differential evolution (DE) optimization which is first of this kind for adsorption applications was implemented to estimate the isotherm parameters in their non-linear form. The model predictions from the DE based optimized parameters provided better predictions and closer to experimental values. The percentage removal of phenol from four different adsorbent dosages with constant initial feed concentrations of phenol found to be varying from 63% to 96% as increase in carbon loading at constant liquid flow rate. These experimental results also revealed that coconut shell based activated carbon is a viable cheaper adsorbent for phenols removal from effluent wastewater.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

Abstract: The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

Durability Investigation of Carbon Nanotube as Catalyst Support for Proton Exchange Membrane Fuel Cell Electrode

Abstract: Abstract Electrochemical surface oxidation of carbon black Vulcan XC-72 and multiwalled carbon nanotube (MWNT) has been compared following potentiostatic treatments up to 168 h under condition simulating PEMFC cathode environment (60 °C, N2 purged 0.5 M H2SO4, and a constant potential of 0.9 V). The subsequent electrochemical characterization at different treatment time intervals suggests that MWNT is electrochemically more stable than Vulcan XC-72 with less surface oxide formation and 30% lower corrosion current under the investigated condition. As a result of high corrosion resistance, MWNT shows lower loss of Pt surface area and oxygen reduction reaction activity when used as fuel cell catalyst support.