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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.

Monday, June 18, 2018


Sunday, June 17, 2018


Saturday, June 16, 2018


Saturday, June 9, 2018

Truck Run 2018

Today, Andy and I joined the yearly Truck Run organized by De Tukker Truckers, just like we did two years ago. The GPS-track of how we drove in KML file for Google Earth.

Friday, June 8, 2018


Saturday, June 1, 2018


Tuesday, May 29, 2018


Monday, May 28, 2018

Three fold symmetry

There are another nine coloured strap sequences that have a three fold symmetry, but all these have at least six cases where a certain colour combinations of straps returns after a day. They are displayed below. I have aligned them such that the 'big' triangle is oriented in the same way, with one vertex on the right. I feel they look different from the sequence that I am using now.

This text is displayed if your browser does not support HTML5 Canvas.

The sequences (from a total of 8,540 unique sequences with respect to permutations of the colours, starting position and direction) where found with the program rubberBands.cpp.


At two meter, the maximum temperature at weather station at Twente Airport was 29.4° Celcius and at 10 cm it was 32.1°. It would not surprise me if these are record high temperatures for this day of the year. In the past week the wind often comes from the East and becomes stronger in the second part of the day.

Monday, May 21, 2018

KunstenLandschap 2018

In the afternoon, I went to KunstenLandschap 2018 (Art and landscape), which is a route along 19 (or so) locations, where some art is on display. I followed the route from the first to the last location. Then I went back to one of the fighter bunker to watch a dance performance by Tess Lucassen and some others. There was also a puzzle quest. There were five locations where you could make yourself woodcut print in the form of a puzzle piece, that when put together formed one artwork of 40 by 60 cm designed by Elsbeth Cochius. I made a KML file for Google Earth of the route that I biked. I met several people that I knew. One of them was Kira Fröse, who had decorated the inside of a small shelter bunker (at location Number 11). I liked the following works the most:

Sunday, May 20, 2018

Three fold rotation symmetry

I thought about a way to visualize the long sequence of coloured rubber straps, and I came up with the following figure:

This text is displayed if your browser does not support HTML5 Canvas.

In this figure there are ten triangles, one for each combination of the five coloured rubber strapts, such that the vertices are on a circle representing the repeated sequence. There are fifteen pairs of parallel lines, where each pair represent two combination occuring in both directions along the sequence. At first sight the figure seems to have some mirror symmetries, but actual it has a three fold rotation symmetry.

Saturday, May 19, 2018

Dairies of Doeschka Meijsing

I finished reading the book En liefde in mindere mate: dagboeken 1961-1987 about the diaries of Doeschka Meijsing, a Dutch novelist. This is part one, as she died in 2012. It seems that the second part has not been published yet. Almost half of the book consists of notes. Some of the notes, contain back ground information that is not really relevant for understanding the diary. The editors of the diaries, made a selection of her diary. They did not give information about the ratio of entries they selected. I felt they might have better included more entries and make the notes more concise. It was an interested read. It does show, as so many biographies before, that people wrestle for many years with problems in their lives and have a very hard time to change there basic habits.

Thursday, May 17, 2018


Wednesday, May 16, 2018


Tuesday, May 15, 2018


Wednesday, May 9, 2018


At 9:52, I bought the following two books from charity shop Het Goed:
  • The Awakening and Selected Short Fiction by Kate Chopin, Rachel Adams, and George Stade (also editor) in English and published by Barnes & Noble in 2005, ISBN:9781593081133for € 1.50.
  • The Awakening - Thrift Study Edition written by Kate Chopin in English and published by Courier Corporation in 2010, ISBN:9780486475660, for € 0.95.
At 17:10, I bought the following seven comics (all in Dutch) from Valérian and Laureline series, drawn by Jean-Claude Mézières after a scenario by Pierre Christin, and published by Dargaud:
  • Ravian: Het woedende water translated from La Cité des eaux mouvantes, ISBN:9032003217, for € 2.50.
  • Ravian: Land zonder sterren translated from Le Pays sans étoile, for € 1.95.
  • Ravian: Het verloren volk translated from Bienvenue sur Alflolol, ISBN:9032003217, for € 1.95.
  • Ravian: De ambassadeur de schaduwen translated from L'Ambassadeur des Ombres, ISBN:9032002368, for € 1.95.
  • Ravian: De vale schepper translated from L'Sur les terres truquées, ISBN:9032002376, for € 2.50.
  • Ravian: Brooklyn station eindpunt cosmos translated from Brooklyn station terminus cosmos, for € 1.95.
  • Ravian: De levende wapens translated from L'Sur les terres truquées, ISBN:9067933147, for € 1.95.

Monday, May 7, 2018


This afternoon, I bought a print of the woodcut 'Droomkoppel' from Willemijn Calis, which I saw on April 14 at the exhibition 'China Dreams'.

Sunday, May 6, 2018


Saturday, May 5, 2018


Friday, May 4, 2018


Thursday, May 3, 2018

Three Dune Books

At 09:49, I bought the following three book from charity shop Het Goed, for € 0.95 each, all written in English and published by New English Library:
  • Dune Messiah written by Frank Herbert, published in 1977, ISBN:9780450032660.
  • Children of Dune written by Frank Herbert, published in 1977.
  • God Emperor of Dune written by Frank Herbert, published in 1981, ISBN:9780450052620,

I have now all books of the Dune series written by Frank Herbert both in English as in Dutch. I have not read all of them in both languages.

Tuesday, May 1, 2018

428,362 sets of equations

I calculated that there are 428,362 sets of equations for the the Irregular Chocolate Bar problem for the problem of finding 22 unique integers which can be divided in up to and including 10 partitions. (This calculation took 13 hours 39 minutes.) So far, my program has searched 62,378 of these sets of equations and found 959 solution with some duplicates resulting in 554 unique solutions. It looks like the program will require some more months to search the remaining sets of equations.

Monday, April 30, 2018


At 09:31, I bought the book Sur Place, Catalogus / Catalogue edited by Maria Anne van Dijk, written in Dutch and English, and published by Fortis Stichting Kunst en Historisch Bezit in 2007, ISBN:9789090216461, from charity shop Het Goed for € 3.50.


Sunday, April 22, 2018

Peterson graph

I thought about making a pendant of the Perterson graph. I had something like the Petersen Graph Pendant in mind, and I thought about making it from a copper wire. Then I wondered if it would be possible to make it out of a single copper wire, where each edge is visited twice in opposite direction. At home I adapted the program I wrote two days ago, because trying this by hand seemed too complicated, and it found 960 'different' solutions of 30 combinations where the minimal distance between two occurences is five. No solutions with a greater minimal distance were found by the program. Five is two less than seven as found with the solution with 20 combinations. I also discovered that 720 of these solutions have five combinations occuring just five positions from each other, and 240 solutions with only three combinations occuring just five positions from each other. There was no further subdivision with respect to the occuring distances between combinations. It would not surprise me if there are basically only a few (two or four) solutions. I have not yet decided whether I am going to switch to the sequence of 30 combinations. Luckily, I can delay the decision till the thirtieth of the month because I found a solution that is similar until that day. The combinations for that sequence are displayed below:

Saturday, April 21, 2018


Friday, April 20, 2018

Coloured rubber straps

About two weeks, I bought a ball of coloured rubber straps, with the intent to use as hair rubber straps. I got the idea to use two straps with different colours every day from a set of five colours. I also do not want to wear the same colour on two consecutive days. I reasoned that there must be a sequence of ten combinations that I could follow (because there are ten combinations of five colours). When I wrote a program to count all the solutions, I discovered that there was none. Next, I searched for a solution of twenty combinations where each combination is included twice, and I found many. In search of an elegant solution, I wanted to avoid solutions where some colour is not used for some time or used on a long sequence of alternating days. Then I realized that I also did not want to wear a certain combination on days that are close together. However, in each solution of twenty combinations, there was a combination that appeared only three days apart. While thinking about this, I realized that the combinations are like the vertices in the Perterson graph. This also explains why there was no solution for ten combinations, because the Peterson graph has no Hamiltonian cycle. I wondered whether anybody ever studied the existence of paths that visit each vertex exactly n-times, a generalisation of Hamiltonian cycles (for which n equals 1). Maybe one reasons is that many graphs that do not have a Hamiltonian cycle do have a cycle which visits each vertex twice, and/or that there exists a rather simple constraint for which a graph contains a cycle that exactly visits each vertex n times. But adding the requirement that each there must be at least k vertices between two consecutive visits, may make it interesting. One could even state that fraction k+1 divided by the number of vertices defines the Hamiltonianess.

When I tried to find an elegant solution on paper, I realized that there was an error in the part of the algorithm that calculated the distance between reoccurences of the same combination of coloured straps. When I corrected the algorithm, it counted 60 solutions with at least seven other combinations between each combination. The solution I had found on paper, was on of the 60 solutions found by the program. I strongly suspect that all solutions are basically the same, with the colours and the starting position permutated, because there are 10 combinations and 3! ways in arranging the neighbours of a certain combination. I wrote a small fragment of JavaScript to calculate, which combination to wear on the coming ten days (from today). (I am not going to publish the program, because it seems I could have figured out everything on paper.)


Thursday, April 19, 2018

AKI takes over

In the afternoon, I went to see the exhibition AKI takes over: "Hotel Bella Arte" at the University of Twente with works by Nils Leibeling and Jelle van Assem.

Almost 30°

At two meter, the maximum temperature at weather station at Twente Airport was 28.7° Celcius and at 10 cm it was 29.9°. It would not surprise me if these are record high temperatures for this day of the year. Most flowers of our magnolia have fallen off. A tulip has opened in the back garden.

Wednesday, April 18, 2018


Tuesday, April 17, 2018


At 16:32:40, I bought the following two books from charity shop Het Goed:
  • Deeltijdopleiding Fine Art Enschede 2011 written in Dutch for € 0.95.
  • Welchen soll ich nehmen? written by Eva Heller in German and published by Ullstein in 2003, ISBN:9783550084157, for € 1.95.

Saturday, April 14, 2018

China Dreams

I saw the exhibition China Dreams by Willemijn Calis at XPO. The works on display were made during her trip to Dalin, China. I found one of the works quite interesting and contacted her.

Friday, April 13, 2018

Easter Egg in the Gigatron

While showing the Gigatron TTL microcomputer to some family members, I hit upon an animation that I had not seen before and that to my knowledge has not been published. I conclude that this must be Easter Egg build into the ROM by Marcel and Walter. I have not yet discovered the exact steps to activate the Easter Egg, but I was able to activate it a second time. I found nothing in the gigatron-rom at GitHub related to the Easter Egg, which seems to imply that the ROM is either different version than the one published there (or that the target files published there are different that the ones produced by the sources). Have fun with you Easter Egg hunt!

Addition Saturday, April 14: I got an email from Marcel informing me that I was the first one to have reported the Easter Egg and that even Walter did not know anything about it.

Tuesday, April 10, 2018


June 2018
May 2018
April 2018
March 2018
February 2018
February 2018
Alzheimer's Disease
Trip to China 2010
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Califlower fractal


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