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About science, and whatever else is on my mind

11 Nov 2021: I got stuck in a revolving door today… and then did it again!

“Suppose we have a revolving door with 4 compartments, each taking up 90 degrees, like in the picture below. There are sensors both inside and outside the building. If a sensor detects a person approaching, the door starts turning. It will turn exactly 180 degrees, and then stop. Is this door safe to use?”

Source: Wikipedia

This exercise comes from a course on concurrency and distributed systems that I used to teach at Oxford. Students would build a model and then check for deadlocks with a model checker. But of course it is way more fun to check this in real life. So when I realised that the revolving doors at ITU were programmed in this exact way, I proceeded to test if I could get myself stuck, and I succeeded. Of course, I had to test if it was not just a fluke. So I tried it again, and succeeded once more. I must have looked like a lunatic walking around in a revolving door, but I was doing it for science! Can you figure out how I got myself stuck?

Source: XKCD

18 Oct 2021: 5 things I noticed moving to Denmark

I recently moved to Denmark to start my first postdoc at the IT University of Copenhagen. Having lived in the Netherlands, UK, and Switzerland before, I was curious how Denmark would be different. Many differences I expected, such as the language, the number of bikes, and traditional cuisine. But here are a few things that I did not expect:

1: There is a lot more space than I expected
Roads are wider than I am used to, with plenty of space for cars, buses, bikes and pedestrians. Especially the newer roads. After living in Oxford and Baden, both quite old cities with narrow streets, it almost feels like I’m in the US. It makes the city feel a lot less crowded than I expected, definitely a plus!

2: Cycling in Copenhagen is stressful
I am from the Netherlands, so cycling in a city with a huge number of fellow cyclists is nothing new to me. But here in Copenhagen, everyone seems to be in extreme haste, trying to get wherever they are going as fast as possible. It almost seems like a race. In the Netherlands, we prefer a more relaxed style where we have a nice chat while cycling home.

3: All the butter and margarine is salted
When asked why, Danes tell me that butter without salt does not taste good. It’s funny because to me, salted butter only tastes nice on plain bread. I don’t find it appealing at all when mixed with sweet bread toppings, such as the Dutch hagelslag. I guess this is a true cultural difference in taste.

4: Liquorice tea is all the rage
The standard tea supply at my office is Earl Grey and Liquorice. In UK and the Netherlands liquorice is more of a special flavour that you typically find in tea collections at home, but not in a standard supply at the office. Supermarkets here also place it among the standard choices, not among the more special flavours of tea. A cultural difference that I don’t mind in the least, I love liquorice tea!

5: It’s hard to get into the system, but once you’re in, everything becomes super easy
So the Danes have this person identification number called a CPR number, and they use it for everything. Everything. Not just government things, also healthcare, banking, and sometimes even your local gym asks for this number. Once you are in this system and have this number (and the online login that comes with it), you only need to give this number to an organisation and authorize access for them, and they will have all the information they need. As in: I did not need to tell my employer my bank account nr for them to be able to pay my salary, they got that information automatically via my CPR. It is wonderfully easy! Of course, privacy is a thing and an organisation will only get access to the information they are entitled to, so my employer cannot see my medical records, but my doctor can.
The downside of this system is that it takes forever to set up. There are a few administrative steps before you can get a CPR number, and everything else (bank, doctor, etc) has to wait until you have your CPR. For comparison: in the UK it took me a week from entering the country to being fully settled with a bank account, doctor, etc. In Denmark, it took me 2 months. But now that I’m in, the easy life can start 🙂



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