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May 2016 Archives

Right. Time to come up for air after a hectic month. I can breathe again, at least until the end of tomorrow, when the next pile of assignments land on my desk for marking.

I bought a new car last week. Well, new for me. The previous 22-year-old piece of machinery had finally succumbed to the effects of old age and high mileage. One coolant leak too many and it was off to the scrapyard for recycling. With the new car came the need for transferring my University of Waikato 'Licence to Hunt' out of one vehicle and into the other.

No, this is not a licence to hunt big game, rabbits, students or other campus life. Come to think of it, I don't ever recall seeing any big game on campus, but there are certainly plenty of rabbits and students around. It's a licence to hunt an on-campus staff parking space, a privelege for which I pay a few dollars a week . Yes, since the beginning of the year we've had to pay to park on campus, although it has to be said there has never been any difficultly in finding somewhere to park.

The licence is a credit-card sized piece of plastic, that sits in a holder, rather like what is used for the registration tag on a car. But pulling the licence out of its plastic holder was actually a bit of a tricky task. Having been sitting on a car windscreen over summer, it was no longer flat. I got it out of one holder, with a bit of tugging,but in its bent condition it certainly wouldn't fit in a new holder and stick on the windscreen of the new car.  What do I do with it?

Having mentioned this to a colleague, the answer was very straightforward. Iron it. Basically repeat the process that caused it to distort in the first place, namely undergoing the 'glass transition'. Thermoplastics, when cold, are hard and brittle. They are in a 'glass' state; they have long chain molecules that are twisted together and can't easily move. But heat it sufficiently, and it reaches a transition point (the 'glass transition') where the long molecules are able to twist and move much more easily. As a result the whole material becomes rubbery and distortable. I don't know exactly what material the permit is made from (I'm sure someone here could tell me), but it's one that clearly has its glass transition at a temperature lower than that exhibited inside a car on a hot day.

So, with a low-heat iron, I ironed my parking permit (Yes, I did put a piece of scrap material on top so it didn't get too hot too quickly). And quite suddenly the whole thing went rubbery. I could have folded  it in half, or scrunched it up. I ironed it nice and flat, then just waited for it to cool. Pretty suddenly, in went from soft and flexible to hard and brittle again. Result: a parking permit that was back to its original condition.

If you want to try this at home I suggest doing some research first and picking the right material. Ironing a credit-card might not be a clever idea.

There are some good YouTube videos of this with various materials, for example this one.

 

 

 

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Probability crops up in many places in physics, not least quantum mechanics and statistical mechanics, where we are only sure of things in an average or 'statistical' sense. Dealing with probabilities can be a headache for many students.

They are also a headache for many in everyday life. There are numerous occasions where we need to estimate the likelihood of something occuring, and we can get it very wrong indeed. What is the probability of encountering a monster traffic jam on the way to Auckland Airport (i.e. just how early should I leave for that flight?).  What are the chances that my visitor will actually turn up on time (or at all?)  However, bookmakers make their living on estimating probabilities, so it's always amusing when they get it wrong. (Plus the fact that I have deep issues with gambling).

So, first, congratulations to Leicester City on winning the English Football Premiership.

At the beginning of the season, so I am led to believe by Radio NZ, one of the major bookmakers in the UK had them as 5000-1 outsiders. That's five THOUSAND to one. Moreover, they thought it more likely, according to the odds that they were offerering,  that in the coming year:

1. Conclusive evidence would be found of the existence of the Loch Ness Monster

2. Barak Obama would declare the moon landings as faked

3. Elvis Presley would be discovered alive

Really? Come on. Yes, Leicester's success was unlikely, but THAT unlikely?  They had a flurry of success right at the end of the 2014-2015 season, to avoid relegation (comfortably in the end), and changed their manager. Hints that things could go well for them the following year. Offering such extremely long odds seems to fly in the face of the evidence that was there. Rank outsiders do occasionally win sporting events, or elections.  It doesn't happen only once every five thousand times.

I remember when I worked in industry in the UK we had an online tool for assessing business opportunities. If we put in a bid to a customer, or a project proposal, or were even having preliminary discussions with a potential customer, we entered the details into a database, including such things as likely size of the contract, and what the probability was of winning it. That would be used to help with our financial planning. However, the reality, as our accountants kept telling us, was that the average person who had discussions with potential customers (for example, myself), was very bad at estimating the probability of success. We tended to severely overestimate the probability. That was evident just from an analysis of what we said were the chances and what actually transpired.

For example, they could pick out the entries where we said there was a 50% chance of securing funding, and look at what fraction were actually funded. It wasn't anywhere near 50%. Given that the organization was full of mathematicians and physicists, this was quite amusing, and it shows how difficult it is to get a real handle on probabilities.

I'm not sure what the accountants did with our estimates, but they probably halved them or more. Which is what I've done with my estimated chance of having my Marsden Proposal get to the second round. I find out later this week.

 

 

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