3 research outputs found
On the correct determination of rotational angles for twisted-profiled sweep objects
In the context of the paper of V. Akman and A. Arslan, "Sweeping with All Graphical Ingredients in a Topological Picturebook" [Computers & Graphics, Vol. 16(3), pp. 273-281, 1992], a new construction of the rotational matrix is presented. This fixes a bug discovered by the first author. © 1994
Improving the validity of shod human footstrike modelling with dynamic loading conditions determined from biomechanical motion capture trials
This thesis presents and evaluates a number of finite element footstrike models developed to
allow the performance of prospective athletic footwear designs to be evaluated in a virtual
environment. Successful implementation of such models would reduce the industry’s
traditional reliance on physical prototyping and therefore reduce the time and associated costs
required to develop a product.
All boundary conditions defined in each of the footstrike models reported were directly
determined from biomechanical motion capture trials to ensure that the loading applied was
representative of shod human running. Similarly, the results obtained with each model were
compared to digitised high speed video footage of experimental trials and validated against
biomechanical measures such as foot segment kinematics, ground reaction force and centre of
pressure location.
A simple model loaded with triaxial force profiles determined from the analysis of plantar
pressure data was found to be capable of applying highly representative load magnitudes but
the distribution of applied loading was found to be less accurate. Greater success at emulating
the deformation that occurs in the footwear during an entire running footstrike was achieved
with models employing kinematic foot segment boundary conditions although this approach
was found to be highly sensitive to the initial orientation of the foot and footwear
components, thus limiting the predictive capacity of such a methodology. A subsequent model
was therefore developed to utilise exclusively kinetic load conditions determined from an
inverse dynamic analysis of an experimental trial and demonstrated the greatest predictive
capacity of all reported models. This was because the kinematics of the foot were allowed to
adapt to the footwear conditions defined in the analysis with this approach.
Finally, the reported finite element footstrike models were integrated with automated product
optimisation techniques. A topology optimisation approach was first utilised to generate
lightweight midsole components optimised for subject‐specific loading conditions whilst a
similar shape optimisation methodology was subsequently used to refine the geometry of a
novel footwear design in order to minimise the peak material strains predicted
Accurate Targeting of Liver Tumors in Stereotactic Radiation Therapy
This doctoral thesis concerns the treatment of liver cancer patients using
external beam radiotherapy. The quality of this treatment greatly depends
on delivering a high radiation dose to the tumor while keeping the dose as
low as possible to surrounding healthy tissues. One of the major
challenges is locating the tumor at the moment of dose delivery. In this
ork, the uncertainty of locating the tumor was investigated. For this
purpose, gold markers were implanted in the liver tissue and visualized on
X-ray images. The markers were used to measure day-to-day tumor mobility
and motion
due to respiration. Furthermore, it was found that major improvements in
the targeting accuracy can be achieved by using the markers for guiding
the treatment procedure