Tag Archives: express train

Stopped in Lime Street

It is a late, slightly muggy, summer afternoon and I am sitting at the window in the last carriage of a train waiting for it to leave Liverpool for London.  So far, it has been a busy day with meetings in the morning at the University’s facility at Daresbury followed by a couple on the main campus before I walked down to Lime Street station.  I stopped for a bite to eat as I travelled from Daresbury to Liverpool; but I am hungry again, so I have a sandwich that I bought in the station.  However, I don’t like to unpack and start eating until the train starts moving, just in case I am on the wrong train or we have to change trains.  Finally, the train starts to move and as it builds up speed I reach for my sandwich.  Suddenly it stops.  My carriage has not even reached the end of the platform.  Station staff appear outside my window talking into their radios.  What’s happened?  Did the train hit someone?  I thought there was a small thud just before we stopped.  But the station staff seem unflustered.  Wouldn’t there be more urgency about their movements if there was a casualty?  We sit in silence for ten minutes before the train starts to move again and the train manager announces that someone pulled the emergency handle because they decided that wanted to get off the train. Why did they want to get off the train?  Did they realise they were trapped on the train to London with someone who was pursuing them?  Was it a police officer who realised that their quarry had jumped off the train just before it set off?  Or, have I been reading too many Eric Ambler stories (see ‘The Mask of Dimitrios‘ or ‘Journey into Fear‘) involving train journeys across Europe?  Maybe it was someone who just decided that they didn’t want to go London after all and didn’t care about inconveniencing several hundred people or paying the fine for improper use of the emergency handle.  But that seems unlikely too or perhaps not…  I contemplate these options as the train accelerates towards London and I munch my sandwich.  It reminds me of a quote from Gillian Tett (in the FT Weekend on June 17/18, 2017) about people believing they have a ‘God-given right that they should be able to organise the world around their personal views and needs instead of quietly accepting pre-packaged options’.

Recognizing strain

rlpoYou can step off an express train but you can’t speed up a donkey. This is paraphrased from ‘The Fly Trap’ by Fredrik Sjöberg in the context of our adoption of faster and faster technology and the associated life style. Last week we stepped briefly off the ‘express train’ and lowered our strain levels by going to a concert given by the Royal Liverpool Philharmonic Orchestra, including pieces by Dvorak, Chopin and Tchaikovsky. I am not musical at all and so I am unable to tell you much about the performances or compositions, except to say that I enjoyed the performances as did the rest of the audience to judge from the enthusiastic applause. A good deal of my enjoyment arose from the energy of the orchestra and my ability to recognise the musical themes or acoustic features in the pieces. The previous sentence was not intended as a critic’s perspective on the concert but a tenuous link…

Recognising features is one aspect of my recent research, though in strain data rather than music. Modern digital technology allows us to acquire information-rich data maps with tens of thousands of individual data values arranged in arrays or matrices, in which it can be difficult to spot patterns or features. We treat our strain data as images and use image decomposition to compress a data matrix into a feature vector. The diagram shows the process of image decomposition, in which a colour image is converted to a map of intensity in the image. The intensity values can be stored in a matrix and we can fit sets of polynomials to them by ‘tuning’ the coefficients in the polynomials. The coefficients are gathered together in a feature vector. The original data can be reconstructed from the feature vector if you know the set of polynomials used in the decomposition process, so decomposition is also a form of data compression. It is easier to recognise features in the small number of coefficients than in the original data map, which is why we use the process and why it was developed to allow computers to perform pattern recognition tasks such as facial recognition.

decompositionSources:

Wang W, Mottershead JE, Patki A, Patterson EA, Construction of shape features for the representation of full-field displacement/strain data, Applied Mechanics and Materials, 24-25:365-370, 2010.

Patki, A.S., Patterson, E.A, Decomposing strain maps using Fourier-Zernike shape descriptors, Exptl. Mech., 52(8):1137-1149, 2012.

Nabatchian A., Abdel-Raheem E., and Ahmadi M., 2008, Human face recognition using different moment invariants: a comparative review. Congress on Image and Signal Processing, 661-666.