In the following:
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.ces.2005.12.007.
The full text of this article is available from http://anziamj.austms.org.au/V47EMAC2005/Watt/home.html.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1007/s10665-006-9059-9.
Abstract
We investigate a reactor network consisting of two chemostats in series.
Previous researchers have compared the performance of a
two-reactor system against a single reactor having the same total
residence time.
In this paper, we suggest that it is more natural to compare
the performance of a cascade against the optimal performance of
a single-reactor system
having the same, or smaller, residence time.
We consider a biological system in which the growth rate is given by a Monod expression with a variable yield coefficient. We find that it is possible for this model to obtain a significant increase in performance by using a two-reactor system. However for the two-reactor system the performance enhancements are achieved when the system reaches a time-invariant steady-state rather than under conditions which produce self-generated oscillations, which was the focus of interest of earlier researchers.
Keywords: Bifurcation; Bioreactors; Modelling; Nonlinear Dynamics; Reaction Engineering; Stability.
M.I. Nelson and H.S. Sidhu. Evaluating the performance of a cascade of two bioreactors. Chemical Engineering Science, 61(10): 3159-3166, 2006.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.ces.2005.12.007.
Abstract
We investigate a model for the treatment of wastewater in the activated
sludge process. This process is based on the aeration of waste water
with flocculating biological growth, followed by the separation of
treated waste water from biological growth. Part of this growth is
then wasted, and the remainder is returned to the system. The
wastewater reactor is assumed to be well mixed, so the mathematical
formulation for this process can be represented by a continuously
stirred tank reactor with recycle. This system is analysed by combining
steady-state analysis with path-following techniques. In practice,
wastewater is treated by a sequence of tanks arranged in series.
By considering the performance of one tank, our work here provides
a benchmark for comparing the performance of multiple tanks.
S.D. Watt, H.S. Sidhu, and M.I. Nelson. Analysis of a model for the treatment of wastewater by the activated sludge process. The Anziam Journal, 47: C1-C18, 2006.
The full text of this article is available from http://anziamj.austms.org.au/V47EMAC2005/Watt/home.html.
Abstract
We investigate a model for the treatment of wastewater in the activated
sludge process. The process is based on the aeration of wastewater
with flocculating biological growth, followed by the separation of
treated wastewater from biological growth. Part of this growth is wasted,
and the remainder returned to the system. The biochemical model
consists of two types of bacteria, sludge bacteria and sewage bacteria,
and two types of ciliated protozoa, free-swimming ciliates
and ciliates attached to sludge flocs. A combination of steady-state
analysis, path following techniques and numerical integration of the
governing equations are used to study the dynamics of this system in
a network of two coupled reactors arranged in a series. We compare
the treatment efficiency for a single tank system with that of a
two-reactor cascade. In the latter scenario the total residence time
is fixed and the residence time in the first reactor is taken to be
a design parameter. Process parameters that ensure optimal performance
are discussed.
H.S. Sidhu, S.D. Watt and M.I. Nelson. Activated sludge wastewater treatment process: Performance comparison between a two-reactor cascade and a single tank. In D. Paterson & B. Young, editors, Proceedings of the 34th Australasian Chemical Engineering Conference, CHEMECA 2006, 6 pages (on CDROM). CCE Conference Management, The University of Auckland, New Zealand, 2006. ISBN 0-86869-110-0.
Abstract
We model the increase in temperature in compost piles or landfill sites
due to micro-organisms undergoing exothermic reactions. The model
incorporates the heat release rate due to biological activity within
the pile and the heat release due to the oxidation of cellulosic
materials. The heat release rate due to biological activity is modelled
by a function which is a monotonic increasing function of temperature
over a particular range and followed by a monotone decreasing
function of temperature. This functionality represents the fact that
micro-organisms die or become dormant at high temperatures. The heat
release due to the oxidation reaction is modelled by the usual manner
using Arrhenius kinetics. The bifurcation behaviour is investigated for
two-dimensional slab geometries to determine the critical sizes of the
compost piles.
H.S. Sidhu, M.I. Nelson, N.A. Ansari and X.D. Chen. Mathematical Analysis of Self-Heating in Compost Piles. In D. Paterson & B. Young, editors, Proceedings of the 34th Australasian Chemical Engineering Conference, CHEMECA 2006, 6 pages (on CDROM). CCE Conference Management, The University of Auckland, New Zealand, 2006. ISBN 0-86869-110-0.
Abstract
The problems associated with presenting mathematical formulae on the World
Wide Web restrict the development of learning resources for students.
In this paper we describe our experience in developing multimedia resources
combining visual and audio components for delivery over the web.
A preliminary analysis of the impact of these resources upon the
achievement of students is also presented. Although
the techniques we have developed have been applied to Higher Education,
they could also be used at the K-12 level. Furthermore, the techniques can
be used in developing resources for other disciplines.
Elahe Aminifar^{p}, Richard Caladine, Anne Porter and Mark I. Nelson. Online Solutions to Mathematical Problems: Combining Video, Audio and Stills on the Web. In T.C. Reeves and S.F. Yamashita, editors, Proceedings of E-Learn 2006. World Conference on E-Learning in Corporate, Government, Healthcare & Higher Education, pages 2-8 (on CDROM), Association for the Advancement of Computing in Education, 2006. ISBN 1-880094-60-6
Abstract
There are many situations in which the critical conditions for thermal
ignition cannot be determined analytically. These include cases
where the chemistry needs to be properly considered, where the
geometry is not just the simplest and where other processes must be
included. In these circumstances, numerical (or at least semi-analytical)
means are used to determine critical conditions for thermal ignition.
Once confronted with a numerical approach to solving a problem,
it is necessary to be a little circumspect about our results and seek
independent means to corroborate them. For this reason,
the present paper reports on the Method of Lines to investigate a recent
reactive hotspot problem which has previously been shown to display
unexpected behaviour and demonstrates the use of sensitivity analysis to
rigorously determine criticality in such a dissipative system
Keywords: Critical conditions, Method of Lines, Thermal ignition.
R.O. Weber, H.S. Sidhu, D.M. Sawade^{u}, G.N. Mercer and M.I. Nelson. Using the method of lines to determine critical conditions for thermal ignition. The Journal of Engineering Mathematics, 56, 185-200, 2006.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1007/s10665-006-9059-9.