In the following:
Abstract
Food processing wastewaters and slurries typically contain high concentrations
of biodegradable organic matter. Before the
wastewater can be discharged the pollutant concentration
must be reduced.
One way to achieve this is through the use of a biological species
(`biomass') that consumes the
organic matter (`substrate').
We investigate biological reactor models in which the growth rate is given by a Contois expression with a variable yield coefficient. We investigate the reduction in pollutant concentration when wastewaters are passed through one of two reactor configurations: a single reactor and 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. It is found that in many cases an optimal reactor cascade may outperform the single reactor by two orders of magnitude.
M.I. Nelson and H.S. Sidhu. Reducing the emission of pollutants in food processing wastewaters. Chemical Engineering & Processing 46(5), 429-436, May 2007.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.cep.2006.04.012.
Abstract
We model the increase in temperature in compost piles or landfill sites due
to micro-organisms undergoing exothermic reactions. The mode incorporates
the heat release 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, T. Luangwilai^{u} and X.D. Chen. Mathematical Modelling of the Self-Heating Process in Compost Piles. Chemical Product and Process Modeling, 2(2), article 8.
This paper is available at http://www.bepress.com/cppm/vol2/iss2/8.
Abstract
We model the increase in temperature in compost piles
due to micro-organisms undergoing exothermic reactions. The model
incorporates two types of heat release: one due to
biological activity;
and the other due to the oxidation of cellulosic materials.
In this study we also include the consumption of oxygen.
We investigate the bifurcation behaviour
and compare the results obtained from
models that includes and exclude oxygen consumption in both
one- and two-dimensional geometries.
H.S. Sidhu, M.I. Nelson and X.D. Chen. A simple spatial model for self-heating compost piles. ANZIAM Journal E, 48, C135-C150, 2007.
This paper is available at http://anziamj.austms.org.au/ojs/index.php/ANZIAMJ/article/view/86
Abstract
We revisit the analysis of a reactor network consisting of two
coupled continuous stirred tank reactors (CSTRs) arranged in series
(Chem. Eng. J. 59 (1995) 169.) The main idea proposed in this earlier
work is to improve process conversion by generating periodic behaviour
in the first reactor (by appropriate choice of design and operational
parameters) which then `forces' the second reactor. The performance of
this cascade system was shown to be greatly enhanced using the above
strategy. In this paper we show some conceptual errors in the analysis in
the original paper. We also show that by employing a systematic
bifurcation analysis, including the use of a path following software,
greater insights can be gained regarding the system's behaviour.
Using these techniques we show that operation and design parameters
can be readily identified to ensure that the cascade has a superior
performance to a single CSTR.
H.S. Sidhu, S.D. Watt, M.I. Nelson and A.K. Ray. Performance improvement and dynamical behaviour analysis of a cascade of two CSTRs. International Journal of Chemical Reactor Engineering, 5: A13, 2007.
This paper is available at http://www.bepress.com/ijcre/vol5/A13.
Abstract
Students commencing science and engineering degrees at the University of
Wollongong are given mathematics skills test in the first and fourth
weeks of session. An evaluation of the results from these tests
indicate that the majority of students' basic mathematical skills
were insufficient to adequately support the prescribed first year
mathematics curriculum. To address this problem a pilot study was set up
to develop video solutions. These solutions permit students to see
the development of each solution in a step-by-step manner. An
audio commentary on each worked solutions assists learning by providing
students with an explanation of the developing solution. Two methods
of video capture were investigated. The first used eBeam, a system to
capture pen strokes from a whiteboard. The second method used a
video camera mounted on a copy stand. We describe the process by which
the video solutions were recorded and describe the educational
environment in which students accessed them. A preliminary analysis
of the impact of this tool on the achievement of students is also
presented.
E. Aminifar^{p}, A. Porter, R. Caladine and M.I. Nelson. Creating mathematical learning resources --- combining audio and visual components. ANZIAM Journal E 47, pp C934-C955, 2007.
This paper is available at http://anziamj.austms.org.au/V47EMAC2005/Aminifar/home.html.
Abstract
Direct-contact heat transfer involves the transfer of heat between two
fluids by bringing them into intimate contact with each other. While one
of the fluids involved is the continuous phase or the `quiescent phase',
the other, which is intimately mixed with the former, is called as
the `dispersed phase'.
The advantage of direct-contact heat transfer is that it
generates a very high value of overall heat transfer coefficient resulting
in higher heat transfer efficiency. This overall heat transfer coefficient
is maximum at the instant when the two fluids (phases) make their
contact. The value of the heat transfer coefficient decreases rapidly
due to the additional heat transfer resistances built up such as the
condensate layer and so on. This rapid process has made experimental
measurement of the initial heat transfer illusive.
So far there has been only one analytic expression that has
been derived to describe this initial process. The same authors also devised
an experimental technique for measuring the direct contact heat transfer
coefficient during this initial phase. However, while the experimental
technique of the aforementioned authors was adequate, their analytical
expression to evaluate the direct-contact heat transfer was incorrect.
In this paper, five mathematical expressions have been presented
for estimation of the direct-contact heat transfer coefficient for
a condensing vapour bubble. Of these, three have been exclusively
derived here and the other two are modifications from the already
existing expressions. Comparisons have been made with the available
experimental results and the physics revealed by the comparisons
are described.
S. Kar^{p}, X.D. Chen and M.I. Nelson. Direct-contact heat transfer coefficient for condensing vapour bubble in stagnant liquid pool. Chemical Engineering Research and Design 85(A3), 320-328, 2007.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1205/cherd06030.
Abstract
The increase in temperature in compost piles/landfill sites due to
micro-organisms undergoing exothermic reactions is modelled.
A simplified model is considered in which only biological self-heating is
present.
The heat release rate due to biological
activity is modelled by a function which is a monotonic increasing
function of temperature
over the range 0<= T<= a whilst
for T>= a it is a monotone decreasing
function of temperature. This functional dependence represents the fact that
micro-organisms die or become dormant at high temperatures.
The bifurcation behaviour is investigated for 1-d and 2-d rectangular slab
geometries.
In both cases there are two generic steady-state diagrams including one in which
the temperature-response curve is the standard S-shaped curve
familiar from combustion problems. Thus biological self-heating,
can cause elevated temperature raises due to jumps in the steady temperature.
This problem is used to test a recently developed semi-analytical technique. For the 2-d problem a four-term expansion is found to give highly accurate results - the error of the semi-analytical solution is much smaller than the error due to uncertainty in parameter values. We conclude that the semi-analytical technique is a very promising method for the investigation of bifurcations in spatially distributed systems.
M.I. Nelson, T.R. Marchant, G.C. Wake, E. Balakrishnan, and X.D. Chen. Self-heating in compost piles due to biological self-heating. Chemical Engineering Science 62(17), 4612-4619, 2007.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.ces.2007.05.018.
Abstract
We investigate an experimentally verified model for the production of
ethanol through continuous
fermentation. Previous studies investigated this model using direct
integration. Such integration is time consuming as parameter regions of
interest can only be determined through laborious and repetitive
calculations. Using techniques from nonlinear dynamical systems theory,
in particular a combination of steady state analysis and path following
methods, practical insights into operating strategies are found. We use
the performance of the reaction scheme in one tank as a benchmark for
comparing the performances of multiple tanks.
S.D. Watt, H.S. Sidhu, M.I. Nelson and A.K. Ray. Analysis of a model for ethanol production through continuous fermentation. ANZIAM Journal E (EMAC2007), 49, C85-C99, 2007.
This paper is available at http://anziamj.austms.org.au/ojs/index.php/ANZIAMJ/article/view/322.
Abstract
We analyse a model for the activated sludge process occurring in a biological
reactor without recycle. The biochemical processes occurring within the
reactor are represented by the activated sludge model number 1 (ASM1).
In the past the ASM1 model has been investigated via direct integration
of the governing equations. This approach is time consuming as parameter
regions of interest (in terms of the effluent quality leaving the plant)
can only be determined through laborious and repetitive calculations.
In this work we use continuation methods to determine the steady-state
behaviour of the system. In particular, we determine bifurcation values
of the residence time, corresponding to branch points, that are
crucial in determining the performance of the plant.
H.S. Sidhu and M.I. Nelson. Mathematical analysis of the activated sludge process for domestic wastewater treatment. In Proceedings of the 35th Australasian Chemical Engineering Conference, CHEMECA 2007, pages 712-720 (on CDROM), Engineers Australia, 007. ISBN 0-858-25844-7.
Abstract
In this paper we model the thermal behaviour of compost heaps in the presence
of micro-organism undergoing oxidative exothermic reactions. For simplicity
we consider a spatially uniform model in which oxidative reactions of the
cellulosic components is ignored. We use singularity theory to investigate
the generic properties of the model. We show that there are two generic
steady-state diagrams including one in which the temperature-response
curve is the standard S-shaped curve familiar from combustion problems.
Such a steady-state diagram contains an elevated temperature branch,
which is the feature of practical interest in facilities such as industrial
compost heaps and municipal tips. Thus biological self-heating can
cause jumps in the steady-temperature. We outline a procedure by which
reasonable values of the kinetic parameters can be estimated.
M.I. Nelson, H.S. Sidhu and X.D. Chen. A spatially uniform model of oxidative self-heating in compost piles. In Proceedings of the 35th Australasian Chemical Engineering Conference, CHEMECA 2007, pages 1673-1683 (on CDROM), Engineers Australia, 2007. ISBN 0-858-25844-7.
Abstract
We investigate a model for the production of ethanol through continuous
fermentation. Earlier studies have shown that by using continuous
fermentation, rather than other methods such as centrifuges and
settling tanks, the productivity can increase markedly. Recently,
we showed that in a single tank the biochemical model possess a rich
variety array of dynamical behaviour, ranging from oscillations,
period-doubling to chaotic behaviour. We use path-following software
to gain insights into the behaviour of the system when a cascade
of either two or three continuously stirred reactors is used.
In particular, we identify design parameters that optimise the productivity
of the system in the different reactor configurations.
S.D. Watt, H.S. Sidhu, M.I. Nelson and A.K. Ray. Improving ethanol production through continuous fermentation. In Proceedings of the 35th Australasian Chemical Engineering Conference, CHEMECA 2007, pages 1862-1869 (on CDROM), Engineers Australia, 2007. ISBN 0-858-25844-7.
Abstract
Modern technologies provide new approaches to tertiary education and
will be an increasing component of the educational experience in
the future. Their use in education poses a significant challenge to
the design and delivery of teaching and learning as many teachers and
students are unfamiliar with them in this context. Over the last decade
there has been a very rapid expansion in the capability and usage of
Information and Communication Technologies (ICTs) in teaching and
learning. To them effectively there is a need to understand how different
ICTs can be applied to learning and teaching. Videoconference,
Access Grid and Web Conference Applications (WCAs) are now available for use
in higher education. The technologies are compared with a view to
recommending which ones to implement for teaching and learning.
E. Aminifar^{p}, R. Caladine, A. Porter and M.I. Nelson. Beyond Videoconference: Increased Functionality to Enhance Media-Rich Interactions in Teaching and Learning. In G. Richards (Editor), Proceedings of World Conference on E-Learning in Corporate, Government, Healthcare, and Higher Education 2007, pages 6985-6990, Association for the Advancement of Computing in Education, Chesapeake, VA, USA, 2007.
Abstract
A wide variety of research techniques have
been applied to gain insights into the processes governing self-heating
of coal. These range from fundamental investigations investigating the
the oxidation mechanism of coal through to research
methods that are used to provide rankings of the propensity of different
coals to self-heat to topics of mining interest such as
the detection and suppression of self-heatings.
In this article we review the gamut of
experimental work relating to self-heating and spontaneous combustion
of coal.
Although we do not cover
mathematical modelling, we include reviews of experimental techniques
that have been used to obtain kinetic parameters for coal oxidation:
an essential input into any mathematical model.
M.I. Nelson and X.D. Chen. Recent experimental work on the self-heating and spontaneous combustion of coal, in G.B. Stracher (editor), Wild Coal Fires: Case Studies from Around the World, Geological Society of America Reviews in Engineering Geology v, XVIII, p 31-83, 2007. http://dx.doi.org/10.1130/2007.4118(04).
Abstract
Access Grid Rooms (AGR) are rooms that draw together suites of technologies
that enable collaboration and sharing across the internet. The sharing
is of video images, interactive whiteboards, sound, document cameras,
files and other applications. These rooms can be used to deliver lectures
and subjects from one campus to other campuses at the same institution
or to share subjects with other institutions across the country or with
international partners. With no experience in teaching mathematics through
the new medium the commitment to engage in teaching via an
AGR was a leap of faith into one or many visions of the future of
Mathematics Education. In this paper we examine the first 24 months from
conception to a plan to install and use an AGR for teaching research and
collaboration in mathematics and the reality of what transpired. The
paper reports on student and staff experiences in using the technology
to take and deliver honours level subjects across three universities
in Australia.
A. Porter, M.I. Nelson, E. Aminifar^{p}, G. Williams, and R.Caladine. Access grid rooms: the plan, the reality. In C.S. Lim, S. Fatimah, G. Munirah, S. Hajar, M.Y. Hashimah, W.L. Gan, and T.Y. Hwa, editors, Proceedings of the 4th East Asia Regional Conference on Mathematics Education 2007 (EARCOME 4), pages 285--291. School of Educational Studies, Universiti Sains Malaysia, 2007. ISBN 978-983-2700-45-46.