Past OCCAM Special Seminar

20 September 2012
10:15
Guy Ramon
Abstract

Composite membranes comprised of an ultra-thin coating film formed over a porous support membrane are the basis for state-of-the-art reverse osmosis (RO) and nanofiltration (NF) membranes, offering the possibility to independently optimize the support membrane and the coating film. However, limited information exists on transport through such composite membrane structures. Numerical calculations have been carried out in order to probe the impacts of the support membrane skin-layer pore size and porosity, support membrane bulk micro-porosity, and coating film thickness and morphology (i.e. surface roughness) on solvent and solute transport through composite membranes. Results suggest that the flux and rejection of a composite membrane may be fine-tuned, by adjusting support membrane skin layer porosity and pore size, independent of the properties of the coating film. Further, the water flux over the membrane surface is unevenly distributed, creating local ‘hot spots’ of high flux that may govern initial stages of membrane fouling and scaling. The analysis provides important insight on how the non-trivial interaction of support properties and film roughness may result in widely varying transport properties of the composite structure. In particular, the simulations reveal inherent trade-offs between flux, rejection and fouling propensity (the latter due to ‘hot spots’), which are purely consequences of geometrical factors, irrespective of materials chemistry.

  • OCCAM Special Seminar
14 September 2012
11:30
to
13:00
Various
Abstract
<ul> <li>Alfonso Bueno - Recent advances in mathematical modelling of cardiac tissue: A fractional step forward</li> <li>Matt Moore - Oblique water entry</li> <li>Matt Hennessy - Mathematical problems relating to organic solar cell production</li> </ul>
  • OCCAM Special Seminar
11 September 2012
10:15
Abstract
<p>Topological defects (TDs) are unavoidable consequence of continuous symmetry breaking phase transitions. They exhibit several universal features and often span apparently completely different systems. Particularly convenient testing ground to study basic physics of TDs are liquid crystals (LCs) due to their softness, liquid character and optical anisotropy. In the lecture I will present our recent theoretical studies of TDs in nematic LCs, which are of interest also to other branches of physics. </p> <p>&nbsp;</p> <p>I will first focus on coarsening dynamics of TDs following the isotropic-nematic phase transition. Among others we have tested the validity of the Kibble-Zurek [1,2] prediction on the size of the so called <i>protodomains</i>, which was originally derived to estimate density of TDs as a function of inflation time in the early universe. Next I will consider nematic LC shells [3]. These systems are of interest because they could pave path to mm sized scaled crystals exhibiting different symmetries. Particular attention will be paid to curvature induced unbinding of pairs of topological defects. This process might play important role in membrane fission processes. &nbsp;</p> <p>&nbsp;</p> <p>[1] W.H. Zurek, <i>Nature</i> <b>317</b>, 505 (1985).</p> <p>[2] Z. Bradac <i>et al., </i>&nbsp;<i>J.Chem.Phys</i> <b>135</b>, 024506 (2011)</p> <p>[3] S. Kralj <i>et al.</i>, &nbsp;<i>Soft Matter</i> <b>7</b>, 670 (2011);<i> </i><b>8</b>, 2460&nbsp; (2012).</p>
  • OCCAM Special Seminar
27 July 2012
11:00
to
13:00
Various
Abstract
<ul> <li>James Herterich&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Mathematical modelling of water purification</li> <li>Paul Roberts&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Mathematical models of retinal oxygen distribution</li> <li>Stephen O'Keeffe&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Mathematical modelling of growth and stability in biological structures</li> <li>Andrey Melnik&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Dynamics of anisotropic remodelling in elastic tissues</li> </ul> <p>&nbsp;</p> <ul> </ul>
  • OCCAM Special Seminar
8 June 2012
11:30
to
13:00
Various
Abstract
<ul> <li>Savina Joseph - Current generation in solar cells</li> <li>Shengxin Zhu - Spectral distribution, smoothing effects and smoothness matching for radial basis functions</li> <li>Ingrid von Glehn - Solving surface PDEs with the closest point method</li> </ul>
  • OCCAM Special Seminar
8 May 2012
10:15
Nicolas Triantafyllidis
Abstract

Stability plays an important role in engineering, for it limits the load carrying capacity of all kinds of structures. Many failure mechanisms in advanced engineering materials are stability-related, such as localized deformation zones occurring in fiber-reinforced composites and cellular materials, used in aerospace and packaging applications. Moreover, modern biomedical applications, such as vascular stents, orthodontic wire etc., are based on shape memory alloys (SMA’s) that exploit the displacive phase transformations in these solids, which are macroscopic manifestations of lattice-level instabilities.

The presentation starts with the introduction of the concepts of stability and bifurcation for conservative elastic systems with a particular emphasis on solids with periodic microstructures. The concept of Bloch wave analysis is introduced, which allows one to find the lowest load instability mode of an infinite, perfect structure, based solely on unit cell considerations. The relation between instability at the microscopic level and macroscopic properties of the solid is studied for several types of applications involving different scales: composites (fiber-reinforced), cellular solids (hexagonal honeycomb) and finally SMA's, where temperature- or stress-induced instabilities at the atomic level have macroscopic manifestations visible to the naked eye.

  • OCCAM Special Seminar

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