News


Riverside path with obstacles

Riverside path with obstacles

April 2018 - A quick evening stroll from the National Resources Wales car park at Gelli Ddu/Black Covert near Trawsgoed. This is just a flat walk through mixed woodland by the side of the Afon Ystwyth. On this occasion, the path was blocked in several places because windblown trees were scattered throughout the forest. This necessitated a few detours to the edge of the woodlands, with views across farmland in the Ystwyth valley. [more external link]  [other news]

Recent beamtime


Selective solvent vapour annealing of diblock films studied by GISANS

Selective solvent vapour annealing of diblock films studied by GISANS

This experiment complements our earlier GISAXS study at DESY, in which we studied the morphological changes in PS-PMMA diblock films under selective solvent annealing. Using neutrons, we were hoping to establish the extent of selectivity of the solvents used towards the two blocks by using H/D isotope contrast. Unfortunately, it turned out that the thin films scattered too weakly to obtain useful scattering patterns over a sufficient q range for quantitative analysis. We are planning a SANS experiment in transmission geometry using several coated substrates stacked in the beam to establish the most promising conditions for changes to the film morphology in preparation of a new attempt at GISANS with much longer exposure. [more] [beamtimes]

Teaching materials


Partial Differential Equations

Partial Differential Equations

I no longer teach this module but have decided to leave the notes online for general reference. Following a brief review of ordinary differential equations, these pages deal with partial differential equations in detail, with applications across physics. Separation of variables, physical boundary conditions and Fourier expansion are introduced using the Laplace equation to determine a temperature profile in a hot plate. These techniques are subsequently transferred to the Poisson, diffusion and wave equations. The lecture ends with an introduction to Fourier transforms.
Dyma fersiwn Cymraeg y tudalennu hyn hefyd. [more] [teaching]

Research papers


Dynamic strain propagation in nanoparticulate zirconia refractory

Dynamic strain propagation in nanoparticulate zirconia refractory

Residual and intrinsic strains in granular materials have been studied extensively. However, understanding the dynamic strains that cause these resultant residual strains is key to developing better strain-resistant materials. This investigation demonstrates a method for characterizing dynamic strain propagation in granular materials. The specimen is a zirconia based refractory composed of sol-gel-derived zirconia nanoparticles in a potassium silicate glass binder. In situ synchrotron X-ray powder diffraction in flat-plate geometry is used to characterize the sample structure on timescales of the order of 1ms. A 125W CO2 laser is used to strain the sample with a 25ms pulse length. To compensate for the poor flux on this timescale, a pump-probe method is repeated 1000 times and the resulting data are subsequently re-binned to improve statistics. A Gaussian weighting function is also used to introduce better contrast between strained and unstrained frames. TOPAS Academic is used for fitting with a Le Bail model in batch mode. Lattice parameters and sample height are refined during fitting, along with a Lorentzian line width for extracting microstrain broadening. Microstrains, epsilon, in the range of 1.01% < epsilon < 1.46% are reported on a 1ms timescale. [request reprint]  [papers]

Walking in Wales


A small circuit into Cwm Rheidol from Pontarfynach/Devil's Bridge

A small circuit into Cwm Rheidol from Pontarfynach/Devil's Bridge

Cwm Rheidol from Pontarfynach/Devil's Bridge
A quick evening wander into the Rheidol gorge, starting from the centre of Pontarfynach/Devil's Bridge, where there is usually ample parking space by the side of the main road. After following the road in the direction of Aberystwyth up to the edge of the village, we took a gate to follow the path over grassland to the edge of the gorge, just above the Vale of Rheidol trackbed. The path then follows along the edge of the wooded slope and alternates between grassland and broadleaf forest. ... [more]
Elenydd  5.4km  230m  2hrs   [more] [walks]

Other diversions


Southampton's old town and cruise docks

Southampton's old town and cruise docks

The day after the Geograph conference 2014, fellow Geograph-er Basher Eyre took us on a guided tour of Southampton's old town. Starting at the station, we walked past the Civic Centre towards the town walls. After seeing an interesting mural summarising Southampton's history in Hamtun Street and hearing about Southampton's oldest church, St Michael's, we saw a number of preserved buildings such as a mediaeval wine merchant's house and the Duke of Wellington pub, passed by the Mayflower memorial and the offices of the Red Funnel ferry company. The tour ended at the ruins of Holy Rood church (now a war memorial), from where we left for tapas in Oxford Street. After the meal, the group scattered and I continued on my own past Bar Gate and the castle wall down to the City Cruise terminal for a close-up of one of the largest passenger ships ever built. After following the Quay roads and the remnants of the town walls at the southern tip of the old town in bright sunshine, I was chased back to the car by an approaching wall of black cloud. I just made it in time! [slideshow] [more] [other diversions]