Interdisciplinary Life Science - PULSe Great research is a matter of choice

Doraiswami Ramkrishna

Doraiswami Ramkrishna Profile Picture

Harry Creighton Peffer Distinguished Professor of Chemical Engineering
Ph.D University of Minnesota (1965)

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Professor Ramkrishna's research group is motivated by ideas in the application of mathematics to solving problems in chemical and biochemical reaction engineering. Their research ideas arise from linear (operator methods) and nonlinear analysis of ordinary and partial differential equations, stochastic processes, and population balance modeling involving integro-partial differential equations.

The current focus in catalytic reaction engineering, in collaboration with Professor Delgass, is in the spatial structuring of catalysts to improve selective conversion in packed bed reactors. The main catalyst is alternately interspersed with a catalyst for an auxiliary reaction system designed to correct unfavorable consequences of the primary reactions such as an inhibitory product, equilibrium limitation or an environmentally hazardous by-product. Current effort is towards assessing the feasibility of maintaining different reaction conditions in contiguous reactor zones with due considerations to reactor sensitivity, possibility of symmetric-breaking spatio-temporal patterns and other nonlinear phenomena.

A distinct aspect of the group's research in biochemical engineering is the cybernetic modeling of regulatory processes in the cells' metabolism with the facility to describe complex substrate-uptake patterns in a multi-substrate environment. Thus cybernetic models have been found to be effective in modeling the growth of hybridoma cells with explanations for the appearance of multiple steady states in continuous cultures. Recent work has shown the utility of cybernetic modeling in metabolic engineering design and targeting genetic changes with global regard to metabolism as a whole.

The destabilization of surfactant-stabilized oil-in-water emulsions is under active investigation using the methodology of population balances and experimental particle size measurements by a Coulter counter. Size distributions from "creaming-free" zones in a creaming have revealed the virtual absence of bulk coalescence in such emulsions implying that the formation of the cream layer occurs mostly by hindered creaming of particles. Hindered creaming of polydisperse emulsions have been investigated using a novel experimental based on population balances and number density measurements in a continuous column.

Precipitation and crystallization processes for the production of fine particles are being investigated with regard to modeling, model identification and, in collaboration with Professor Frank Doyle of the University of Delaware, control of particle size distributions. Current effort is towards the extraction of nucleation and growth kinetics of particles based on dynamic measurements of particle size distributions using discretization procedures and inverse problem methodologies. Preliminary studies of model-based control of particle size distributions in the precipitation of calcium carbonate have also been made.

Selected Publications:

Ramkrishna, D., and A. W. Mahoney, "Population balance modeling. Promise for the future", Chem. Eng. Sci., 57 (4): 595-606 FEB 2002.

Namjoshi, A.A. and D. Ramkrishna, "Multiplicity and stability of steady states in continuous bioreactors: dissection of cybernetic models," Chem. Eng. Sci. Mashelkar Issue, 56 (19), 5593-5607, 2001

Cote, A.S., Delgass, W.N. and D. Ramkrishna, "Spatially patterned catalytic reactors. Feasibility issues" Chem. Eng. Sci., 56 (3): 1011-1019 FEB 2001.

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