Past Industrial and Interdisciplinary Workshops

13 June 2014
11:00
Several Members from DuPont
Abstract
The four topics are: 1. Thermal interface materials 2. Low temperature joining technology 3. Nano Ag materials 4. Status of PV technology
  • Industrial and Interdisciplinary Workshops
6 June 2014
10:00
Andy Stove (Thales)
Abstract
An important military task in a high-technology environment is to understand the set of radars present in it, since the radars will be, to a greater or lesser extent, indicative of the ships, aircraft and other military units which are present. The transmissions of the different radars typically overlap in most of the dimensions which characterise then, such as frequency and bearing, and their pulses are interleaved in time. If, however, we are able to separate the individual pulse trains which are present then not only does this allow us to know how many different radars are present, but the characteristics of the pulse train are indicative of the type of the radar. The problem of recognising the pulse trains is not trivial, because many radars 'jitter' their transmissions and pulses may be missing or two pulses may occur together, causing the characteristics of the pulse to be 'garbled.' The jittering may be used as a way to reject mutual interference between the radars, to resolve ambiguities in measurements of range or velocity or to make it harder to jam the radar. The problems caused by pulses overlapping are likely to become more severe in the future because the pulses of the individual radars are becoming longer. Although solutions currently exist which can cope, to at least some extent, with most of these issues, the purpose of bringing this topic to the seminar is to allow a fresh look at the problem from first principles.
  • Industrial and Interdisciplinary Workshops
16 May 2014
10:00
Ian Wilkinson (Siemens Magnet Technology)
Abstract
NbTi-based superconducting wires have widespread use in engineering applications of superconductivity such as MRI and accelerator magnets. Tolerance to the effects of interactions with changing (external) magnetic fields is an important consideration in wire design, in order to make the most efficient use of the superconducting material. This project aims to develop robust analytical models of the power dissipation in real conductor geometries across a broad frequency range of external field changes, with a view to developing wire designs that minimise these effects.
  • Industrial and Interdisciplinary Workshops
9 May 2014
10:00
Chris Farmer and John Ockendon
Abstract
<p>Seismic exploration in the oil industry is one example where wave equations are used as models. When the wave speed is spatially varying one is naturally concerned with questions of homogenisation or upscaling, where one would like to calculate an effective or average wave speed. As a canonical problem this short workshop will introduce the one-dimensional acoustic wave equation with a rapidly varying wave speed, perhaps even a periodic variation. Three questions will be asked: (i) how do you calculate a sensible average wave speed (ii) does the wave equation suffice or is there a change of form after averaging and (iii) if one can induce any particular excitation at one end of a finite one-dimensional medium, and make any observations that we like at that end, what - if anything - can be inferred about the spatial variability of the wave speed?</p>
  • Industrial and Interdisciplinary Workshops
14 March 2014
10:00
Nick Hall Taylor, Ian Hewitt and John Ockendon
Abstract
This topic was the subject of an OCIAM workshop on 8th March 2013 given by Nick Hall Taylor . The presentation will start with a review of the physical problem and experimental evidence. A mathematical model leading to a hydrodynamic free boundary problem has been derived and some mathematical and computational results will be described. Finally we will assess the results so far and list a number of interesting open problems. ---------------------------------------------------------------------------------------------------------------------------------------------------- After the workshop and during coffee at 11:30, we will also give a preview of the upcoming problems at the Malaysian Study Group (Mar. 17-21). Problem descriptions can be found here: www.maths.ox.ac.uk/~trinh/2014_studygroup_problems.pdf.
  • Industrial and Interdisciplinary Workshops
7 March 2014
10:00
John Rhys (The Oxford Institute for Energy Studies)
Abstract
This talk is intended to explain the link between some relatively straightforward mathematical concepts, in terms of linear programming and optimisation over a convex set of feasible solutions, and questions for the organisation of the power sector and hence for energy policy. Both markets and centralised control systems should in theory optimise the use of the current stock of generation assets and ensure electricity is generated at least cost, by ranking plant in ascending order of short run marginal cost (SRMC), sometimes known as merit order operation. Wholesale markets, in principle at least, replicate exactly what would happen in a perfect but centrally calculated optimal dispatch of plant. This happens because the SRMC of each individual plant is “discovered” through the market and results in a price equal to “system marginal cost” (SMC), which is just high enough to incentivise the most costly plant required to meet the actual load. More generally, defining the conditions for this to work - “decentralised prices replicate perfect central planning” - is of great interest to economists. Quite apart from any ideological implications, it also helps to define possible sources of market failure. There is an extensive literature on this, but we can explain why it has appeared to work so well, and so obviously, for merit order operation, and then consider whether the conditions underpinning its success will continue to apply in the future. The big simplifying assumptions, regarded as an adequate approximation to reality, behind most current power markets are the following: • Each optimisation period can be considered independent of all past and future periods. • The only relevant costs are well defined short term operating costs, essentially fuel. • (Fossil) plant is (infinitely) flexible, and costs vary continuously and linearly with output. • Non-fossil plant has hitherto been intra-marginal, and hence has little impact The merit order is essentially very simple linear programming, with the dual value of the main constraint equating to the “correct” market price. Unfortunately the simplifying assumptions cease to apply as we move towards types of plant (and consumer demand) with much more complex constraints and cost structures. These include major inflexibilities, stochastic elements, and storage, and many non-linearities. Possible consequences include: • Single period optimisation, as a concept underlying the market or central control, will need to be abandoned. Multi period optimisation will be required. • Algorithms much more complicated than simple merit order will be needed, embracing non-linearities and complex constraints. • Mathematically there is no longer a “dual” price, and the conditions for decentralisation are broken. There is no obvious means of calculating what the price “ought” to be, or even knowing that a meaningful price exists. The remaining questions are clear. The theory suggests that current market structures may be broken, but how do we assess or show when and how much this might matter?
  • Industrial and Interdisciplinary Workshops
7 February 2014
10:00
Lia Verhoeff (Chemistry, Oxford)
Abstract

Droplet snap-off and coalescence are very rich hydrodynamic phenomena that are even richer in liquid crystals where both the bulk phase and the interface have anisotropic properties. We studied both phenomena in suspensions of colloidal platelets with isotropic-nematic phase coexistence.

We observed two different scenarios for droplet snap-off depending on the relative values of the elastic constant and anchoring strength, in both cases markedly different from Newtonian pinching.[1] Furthermore, we studied coalescence of nematic droplets with the bulk nematic phase. For small droplets this qualitatively resembles coalescence in isotropic fluids, while larger droplets act as if they are immiscible with their own bulk phase. We also observed an interesting deformation of the director field inside the droplets as they sediment towards the bulk phase, probably as a result of flow inside the droplet. Finally, we found that mutual droplet coalescence is accompanied by large droplet deformations that closely resemble coalescence of isotropic droplets.[2]

[1] A.A. Verhoeff and H.N.W. Lekkerkerker, N. J. Phys. 14, 023010 (2012)

[2] M. Manga and H.A. Stone, J. Fluid Mech. 256, 647 (1993)


  • Industrial and Interdisciplinary Workshops

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