206 research outputs found
The buffered chemostat with non-monotonic response functions
We study how a particular spatial structure with a buffer impacts the number
of equilibria and their stability in the chemostat model. We show that the
occurrence of a buffer can allow a species to persist or on the opposite to go
extinct, depending on the characteristics of the buffer. For non-monotonic
response functions, we characterize the buffered configurations that make the
chemostat dynamics globally asymptotically stable, while this is not possible
with single, serial or parallel vessels of the same total volume and input
flow. These results are illustrated with the Haldane kinetic function.Comment: 9th IFAC Symposium on Nonlinear Control Systems (NOLCOS 2013),
Toulouse : France (2013
A modeling approach of the chemostat
Population dynamics and in particular microbial population dynamics, though
they are complex but also intrinsically discrete and random, are conventionally
represented as deterministic differential equations systems. We propose to
revisit this approach by complementing these classic formalisms by stochastic
formalisms and to explain the links between these representations in terms of
mathematical analysis but also in terms of modeling and numerical simulations.
We illustrate this approach on the model of chemostat.Comment: arXiv admin note: substantial text overlap with arXiv:1308.241
Minimal-time bioremediation of natural water resources
We study minimal time strategies for the treatment of pollution of large
volumes, such as lakes or natural reservoirs, with the help of an autonomous
bioreactor. The control consists in feeding the bioreactor from the resource,
the clean output returning to the resource with the same flow rate. We first
characterize the optimal policies among constant and feedback controls, under
the assumption of a uniform concentration in the resource. In a second part, we
study the influence of an inhomogeneity in the resource, considering two
measurements points. With the help of the Maximum Principle, we show that the
optimal control law is non-monotonic and terminates with a constant phase,
contrary to the homogeneous case for which the optimal flow rate is decreasing
with time. This study allows the decision makers to identify situations for
which the benefit of using non-constant flow rates is significant
About overyielding with mixed cultures in batch processes
International audienceThis paper investigates-via modeling-several possible explanations of overyielding observed in mixed cultures cultivated in batch reactors. It is first shown that the classical model of competition of N species for a single resource cannot explain such overyielding. Then, three hypotheses are introduced and discussed at the light of numerical simulations
Global stabilization of the chemostat with delayed and sampled measurements and control
International audienceThe classical model of the chemostat with one substrate, one species and a Haldane type growth rate function is considered. The input substrate concentration is supposed to be constant and the dilution rate is considered as the control. The problem of asymptotically stabilizing an equilibrium point of this system in the case where the measured concentrations are delayed and piecewise constant with a piecewise constant control is addressed
Contrôle de paramètres dans un chémostat
International audienc
Analysis of a mathematical model of syntrophic bacteria in a chemostat
A mathematical model involving a syntrophic relationship between two
populations of bacteria in a continuous culture is proposed. A detailed
qualitative analysis is carried out. The local and global stability analysis of
the equilibria are performed. We demonstrate, under general assumptions of
monotonicity, relevant from an applied point of view, the asymptotic stability
of the positive equilibrium point which corresponds to the coexistence of the
two bacteria. A syntrophic relationship in the anaerobic digestion process is
proposed as a real candidate for this model
About biomass overyielding of mixed cultures in batch processes
International audienceWe study mechanisms that can produce an increase of biomass production in batch processes when considering mixed cultures, compared to pure cultures. We show that growth thresholds or variable yields can produce 'overyielding', while this is not possible in the classical batch model with multiple species. We give sufficient conditions on the characteristics of the species to obtain overyielding, and illustrate these theoretical results with numerical simulations. This work provides new insights on species complementary in models of mixed cultures, without having to consider direct interactions terms between species as, for instance in the well known Generalized Lotka-Volterra model
About biomass overyielding of mixed cultures in batch processes
We study mechanisms that can produce an increase of biomass production in batch processes when considering mixed cultures, compared to pure cultures. We show that growth thresholds or variable yields can produce 'overyielding', while this is not possible in the classical batch model with multiple species. We give sufficient conditions on the characteristics of the species to obtain overyielding, and illustrate these theoretical results with numerical simulations. This work provides new insights on species complementary in models of mixed cultures, without having to consider direct interactions terms between species as, for instance in the well known Generalized Lotka-Volterra model
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