College of Engineeringhttp://hdl.handle.net/10092/12016-02-12T01:17:26Z2016-02-12T01:17:26ZSpatial Moment Models for Collective Cell BehaviourBinny, Rachelle Naomihttp://hdl.handle.net/10092/117962016-02-10T14:01:04Z2016-01-01T00:00:00ZSpatial Moment Models for Collective Cell Behaviour
Binny, Rachelle Naomi
The ability of cells to undergo collective movement plays a fundamental role in tissue
repair, development and cancer. Interactions occurring at the level of individual cells may
give rise to spatial structure, such as clustering, in a moving population. In vitro cell culture
studies have shown that the presence of such spatial structure can play an important role in
determining the dynamics of migrating cells at a population level. However, mathematical
models that consider population-level behaviour often take a mean-field approach, which
assumes that individuals interact with one another in proportion to their average density and
neglects the effects of spatial structure.
In this work, we develop a lattice-free individual-based model (IBM) for collective movement
in one-dimensional space. The IBM uses random walk theory to model the stochastic
interactions occurring at the scale of individual migrating cells. In particular, our model
allows an individual's direction of movement to be affected by interactions with other cells
in its neighbourhood, providing insights into how directional bias generates spatial structure.
As an alternative to the mean-field approach, we employ spatial moment theory to
develop a population-level model which accounts for spatial structure and predicts how these
individual-level interactions propagate to the scale of the whole population. The IBM is used
to derive an equation for dynamics of the second spatial moment (the average density of
pairs of cells) which incorporates the neighbour-dependent directional bias and we solve this
numerically for a spatially homogeneous case.
Extending our model to consider cell behaviour in two-dimensional space makes it more
amenable for use alongside experimental data. Using imaging data from in vitro experiments,
we estimate parameters for the two-dimensional model and show that it can generate similar
spatial structure to that observed in a 3T3 fibroblast cell population. Finally, we incorporate
cell birth and death into our two-dimensional model to consider how these processes give rise
to spatial structure and how, in turn, this spatial structure affects the collective dynamics.
2016-01-01T00:00:00ZDynamic Behaviour of LVL-Concrete Composite Flooring SystemsAbd Ghafar, Nor Hayatihttp://hdl.handle.net/10092/117952016-02-10T14:01:07Z2015-01-01T00:00:00ZDynamic Behaviour of LVL-Concrete Composite Flooring Systems
Abd Ghafar, Nor Hayati
An LVL-concrete composite floor (LCC) is a hybrid flooring system, which
was adapted from a timber-concrete composite (TCC) floor system. By replacing the
timber or glulam joists with LVL joists, the strength of the floor was increased.
However, the demand nowadays is to build longer spans and this may reduce the
stiffness and lead to the floor being more susceptible to vibration problems.
While the vibration problem may not be as critical as other structural issues,
people could feel sick and not comfortable if the floor vibrates at the resonant
frequency of the human body. Hence, this research focuses on the dynamic behaviour
of long span LCC flooring systems. Experimental testing and finite element modelling
was used to determine the dynamic behaviour, with particular regard to the natural
frequency, fn and mode shape of an LCC floor.
Initially, a representative series of LVL-concrete composite specimen types
were built starting from (1) full-scale T-joist specimens, (2) reduced-scale (one-third)
multi-span T-joist specimens and (3) reduced-scale (one-third) 3m x 3 m floor. The
specimens were tested using an electrodynamic shaker. The SAP 2000 finite element
modelling package was used to model and evaluate the full- and reduced-scale LVLconcrete
composite T-joist experimental results. Additionally, a 8m x 7.8 m LCC floor
was modelled and analysed using SAP 2000. The behaviour of the 8m LCC floor was
investigated through the changing of (1) concrete topping thickness, (2) depth of LVL
joist, (3) different types of boundary conditions, and (4) the stiffness of the connectors.
Both the experimental results and the finite element analyses agreed and
showed that increased stiffness increased the natural frequency of the floor, and the
boundary conditions influenced the dynamic behaviour of the LCC floor. Providing
more restraint increased the stiffness of the floor system. The connectors' stiffness did
not influence the dynamic performance of the floor.
The study outcomes were based on a 8 Hz natural frequency limitation where
the fundamental natural frequency of the LCC floor must exceed 8 Hz in order to
prevent vibration problems. The research showed that a 8 m LCC long span floor can
be constructed using LVL joists of between 300 mm to 400 mm depth with a concrete
thickness of 65 mm for the longer spans, and joists of between 150 mm to 240 mm
depth in conjunction with a concrete topping thickness of 100 mm for the shorter spans.
2015-01-01T00:00:00ZNon-conventional Technologies as Alternative Solutions to the Proposed Whakamaru-Otahuhu Transmission UpgradeO'Brien, R.Hume, D.Bywater, I.http://hdl.handle.net/10092/117872016-02-09T14:00:59Z2006-01-01T00:00:00ZNon-conventional Technologies as Alternative Solutions to the Proposed Whakamaru-Otahuhu Transmission Upgrade
O'Brien, R.; Hume, D.; Bywater, I.
This commentary brings together a preliminary view of the potential of non-conventional generation as a comprehensive alternative solution to the proposed Auckland transmission upgrade.
2006-01-01T00:00:00ZWorkshop : Future Network Security of Supply Requirementshttp://hdl.handle.net/10092/117862016-02-09T14:00:56Z2007-01-01T00:00:00ZWorkshop : Future Network Security of Supply Requirements
2007-01-01T00:00:00Z