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I write, therefore I am

With this variation on a famous statement by the philosopher Descartes, I would like to express that the act of writing about what happens in my life is important to me.

Sunday, February 18, 2018

Black Mirror

In the afternoon, I went to the opening of the exhibition Black Mirror with photographs by Jenny Boot at Fotogalerie Objektief in Enschede.

Saturday, February 17, 2018

Counting Digital Sheep

In the afternoon, I visited TETEM art space. I saw the new exhibition Counting Digital Sheep. Quite interesting. Especially code / coat by Jochem van Schip Artificial Dumpness, and Linger by Japser van Loenen. (Through the latter, I also found eps8266-sniffer when at home.) I also watched In the Robot Skies short film by Liam Young.

Tuesday, February 13, 2018


At 10:14:23, I bought the CD Interstellar: Original Motion Picture Soundtrack from bookshop Broekhuis for € 9.99.

Saturday, February 10, 2018

The MacMahon Squares

Yesterday, I read about Jigsaw Puzzles and The MacMahon Squares, and decided to give it a try. My first idea was to convert the problem to an Exact Cover problem. However, it did not find any solutions. This made me think about a program that could find the best almost solution. When I finished the program, it found 46 solutions. After some debugging, I found a bug in the algorithm to generate an Exact Cover and my Exact Cover solver found the 46 solutions with a second. I combined both algorithm is one program. The 46 solutions are given below:

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Friday, February 9, 2018


Wednesday, February 7, 2018

Natural well

For some week, there has been some water flowing across the bicycle path along the road called Hendrik Ter Kuilestraat at a location that I talked about before. This morning, I noticed that the water was coming from one spot and I stopped to take the picture shown on the right. You can just see the water flowing. A little further on the road, there are also some wet spots, which have turned into ice due to the low temperatures of the past days.


At 12:00, I bought the book following books from charity shop Het Goed:
  • Rijksaankopen: 1985 edited by Evelyn Beer, written in Dutch, and published by Rijksdienst Beeldende Kunst in 1986, ISBN:907146508X, for € 2.95.
  • Rijksaankopen 1987: werk van hedendaagse beeldende kunstenaars edited by Ruud Schenk, written in Dutch, and published by Rijksdienst Beeldende Kunst in 1988, ISBN:9789012059084, for € 2.95.
  • Made in Tilburg written by Caroline Boot in Dutch and published by Nederlands Textielmuseum in 2004, ISBN:9070962349, for € 2.95.
  • Doen jullie het nog?: seks en liefde in relaties written by Jean-Pierre van de Ven in Dutch and published by Ambo/Anthos B.V. in 2012, ISBN:9789026326585, for € 4.50.

150 year Broekhuis

At the end of the afternoon, I visited bookshop Broekhuis, which was established exactly 150 years ago. Five years ago, I bought a book when they celebrated their 145 years existence. The bookshop is still at the same location and has undergo some improvements in the past five years. I did not buy anything.

Friday, February 2, 2018

Bring Your Own Beamer

This evening, I attended the last Bring Your Own Beamer event at Tetem art space. The event was similar to last years. I occupied the same spot with an updated version of the project based on Street Tiling Patterns and a projection of a negative of an old picture of Li-Xia by the parts of the beamer that I put together last Tuesday and finished Wednesday evening. A picture of this is shown on the top right. For the Street Tiling Patterns project, I increased the speed of the animation and I removed a bug in the algorithm to find a matching pattern. There were some people from last year. One of them was Willemijn Calis. I also met Tessa Langeveld, who was showing moving forms in still spaces. A lot of people from TkkrLab came to visit and two of them had brought their own projects.

Before the visitors came at eight, I started working on the idea to pick the colours for the Street Tiling Patterns project from a limited palette as inspired by the colour palettes by Peter Struycken. At home, I continued working on this, resulting in the following palette:

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Tuesday, January 30, 2018

BYOB preperations

This evening, at TkkrLab, I spend some time preparing for coming Fridays "Bring Your Own Beamer" event. First I tested my notebook with a beamer to see if it worked with the updated version that I showed on last years event. Basically, I have made it run faster, because it was changing to slow to be noticed by people just giving it a short look, and I fixed a bug, which prevented one of the effects not to work properly. Next I played with some parts of an old beamer, which I found on January 24, 2017. Some other member told me that he still had the lens to go with it and showed where it fit, which made me realize that I was totally wrong about how it worked. At some point, because I did not have the right lamp, I decided to leave it for home and work a little on my notebook. At home, I did some further experimentation and got some idea of how I am going to use it.

Monday, January 29, 2018


At 10:08, I bought the book Examencatalogus Yeahboek 12|13 written in Dutch and published by AKI ArtEZ on Thursday, June 27, 2013 from charity shop Het Goed for € 2.50. Later, I discovered I already bought a copy of this book on Saturday, November 18, 2017. On the front page there is a dedication by Sumchog Kersbergen, also with a line in the Devanagari script.

Thursday, January 25, 2018


At 10:41:44, I bought the book Atlas of Remote Islands: Fifty Islands I Have Not Visited and Never Will written by Judith Schalansky in English and published by Particular in 2010, ISBN:9781846143489, from bookshop Broekhuis for € 19.95. At 11:12:05, I bought Issue 2 of year 2007 of the Dutch art magazine Metropolis M from charity shop Het Goed for € 0.50.

Wednesday, January 24, 2018

13.7° Celcius

Between 14:30 and 15:00, the temperature at the closest official weather station was 13.7° Celcius, which is a record high for this day as long as records have been kept.

Opening "Maß und Ziel"

In the evening, I went to the opening of the exhibition Maß und Ziel with works by Carina Schüring. The exhibition was held in the Old Town Hall in Neuenhaus where Carina grew-up and no lives again. The room was full of people, mostly with people from Neuenhaus. I guess, I was the only Dutch person around. But I met some Germans, especially those who studied in Enschede, who could speak Dutch. I could understand most of the introduction by Anke Baumeister. Only after about half of the people had left, I could find some time to study her new works. From a distance they often do not look that interesting, but when you come closer and closer, the more interesting it becomes. I really feel that the quality of her work has matured a lot in the past year. I feels as if she has found the quietness to search deeper.

Tuesday, January 23, 2018

Cordwoord puzzle too

At TkkrLab I found a Cordwoord puzzle too in a box we received from the Electronics Research Group · University of Aberdeen. I decided to give it a try and spend the rest of the evening studying it and performing some soldering. I am about halfway and left it in my box in the space for another day.

Thursday, January 18, 2018


Wednesday, January 17, 2018

Some snow

Around seven in the morning, I saw some snow on the cars, but not on the ground. Around eight, I saw that it was snowing. When went outside around half past eight, it was snowing. I measured 1.5 cm of snow on the table outside. Around ten, the snow already started to melt. It snowed on and off during the day. In the evening there were still some patches of snow, mostly on (high) grass.

Tuesday, January 9, 2018

New bike

This morning, I went to get my new bike, a Vilo de ville B 200 in the colour apple green. Instead of a chain drive it has a belt drive, which is more durable, maintenance free, very silent, and has less friction.

Monday, January 8, 2018

You are what you do

This morning, I finished reading the Dutch book Je bent wat je doet (You are what you do) by Roos Vonk, which I started reading on December 20, 2017, the day I bought the book. Roos Vonk is a Dutch professor of social psychology. What I like about the book, compared to other self-help books, is that it contains many references to scientific experiments to support the advice that it gives. It is also a very practical book. Although I have finished reading the book, I am going to study again, trying to make a summary of the main points in order to apply them to my own life.

Four colour theorem: edge marking

The Four colour theorem states that faces of a planar graph can be coloured with four colours. Given four colours, there are 24 ways to permute them. Because of this, there must be another method to represent a colouring with less freedom. For each planar graph with degree three it is possible to define an equivalence relationship between a face colouring and an edge colouring with three colours. Given three colours, there are six ways to permute them. Which gives reason to believe there is a more compact way to represent a colouring. And there is indeed, because with each edge colouring it is the case that at each vertex the three edges are assigned a different colour. By assigning a number to the edge colours, the colours will appear either clockwise or anti-clockwise around each vertex. This can be represented by assigning one of two 'colours' to each vertex. One could exchange these, meaning that there must still be a more compact method for representing a face colouring of a planar graph with degree three. This can done by marking the edges for which the edge colours around the vertices of the edge run in a different direction. It appears that for a marked edge, the colours of the faces on the 'opposite side' of the two vertices are always the same, while for an unmarked edge they are always different. The edge marking also has the property that each face has an even number of edges with a marking. But that is about everything that can be stated in general. Depending on the number of edges of a face, there are certain patterns of edge markings that are allowed, but there are no simple rules to describe which patterns can occur.

The Philosophy of Andy Warhol

This evening, I finished reading the book The Philosophy of Andy Warhol by Andy Warhol, which I started reading on December 9. 2017 after I bought it on November 26. I found this a rather boring book. It is rather similar to A, A novel in the sense that it present every day talk as something special. It has long transcripts of telephone calls with B, who according to Pat Hackett is Brigid Berlin. It is definitely not about philosophy, at most about Warhol's attitude to life.

Sunday, January 7, 2018

Persistent 'balanced' tree

In the past weeks, I worked on the implementation of a persistent tree data structure. I first wanted to base it on a red-black tree, but then decided on a kind of 'balanced' trees using an extra height indicator. The idea is that this would also allow less optimal height differences in favour of sharing larger parts between versions, by only performing the balancing in the parts that made version specific. This afternoon, I finished a first version, which works correctly and keeps the tree reasonable balanced under deletion, but does not implement the idea of sharing larger parts between versions. I still would like to perform some performance analyses to see if it can be optimized. All the code is in a single file, which also includes all the testing procedures and some debugging code.

Thursday, January 4, 2018

Random Street Tile Pattern

I found a way to prevent the errors. I realized that there were squares of four values that did not match the allowed tiles. I added a check to the program enforcing this. Still there are some problems at the borders, which I hide by showing only part of them. More research will be needed to address these issue.

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Wednesday, January 3, 2018


February 2018
January 2018
December 2017
November 2017
October 2017
Alzheimer's Disease
Trip to China 2010
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