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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, October 7, 2019

Checking maze

I am working on a program for generating mazes and I wanted to implement an algorith to check if a maze is 'nice', meaning that from every 'room' you can reach any other 'room' and that there is exactly one route between any two rooms, or in other words, that you cannot walk in a circle. (In graph theory the nice maze is similar to a tree graph.) I was thinking about all kinds of rather complicated algorithms to check these properties, until I realized that there was a very simple algorithm. This algorithm depends on the property that you can walk through a maze by following the wall on your right (or left) side. With a closed maze, you will return to where you started. If the maze is nice, you will visit every passages (between two rooms) in both directions. The number of passages for a nice mazes is one less than the number of rooms and thus easy to calculate. If the maze is not nice the number of passages you pass while following the wall will be lower than twice the number of passages. If some rooms are not reachable from each other, you will not visite them during the walk, and thus the number of passages you count will be lower. If all the rooms are connected, but you can walk in a circle, than you will never be able to walk around and touch all the walls, meaning that you will only follow some passages in one direction and not two directions. Thus the number of passages you pass will also be lower.


Wednesday, October 2, 2019

Mixed (up)

In the evening, I went to the opening of the exhibition Mixed (up) at B93 with photographs by Esmee van Zeeventer and Patric Jonkman. I talked a bit with Esmee and told her that I am interested in buying a copy of the (small) book she wants to make with some of her photographs. I also talked with one of her former teachers about photography and art.

Sunday, September 29, 2019

Fotomanifestation Enschede

I joined the opening walk of Fotomanifestation Enschede. The theme of this photo manifestation is Inner Circle. The first exhibition is Sistaaz of the Castle by Jan Hoek at Fotogalerie Objektief. It is about seven transsexuals in Cape Town. In the galery there were also small mobile gardens in old soccer balls or baskets. The organization to support them is Support Sistaazhood. Next we went to Concordia for the exhibition What Goes Up by Sylvie Zijlman. Upstairs, I also had a look at the exhbition Untitled Surface by Filip Markiewicz and watched part of the movie Fake Fiction. At bookshop Broekhuis, the exhibition Geachte Afwezige... with photographs by Paul Hajenis was opened. At Rijksmuseum Twenthe, there were two exhibitions part of the walk: Where Will We Go by Kadir van Lohuizen and Setting The Stage by Eddo Hartmann. From this last exhibition, I did like the picture Housewife Somun Street, Pyongyang, 2015 the most. While at the museum, I walked through the exhibition Tischbein en de ontdekking van het gevoel but did not pay much attention. I did get interested by the associated exhibition by Melanie Bonajo, the photo collage Thank you for hurting me. I really needed that... and some video. I also had a second look at the exhibition of works by Peter Zegveld and verified that some of the horns in one of his installations were in the incorrect order. Of course, I also took some time to look at Falaises près de Pourville by Claude Monet and Gezicht op Louveciennes in de herfst by Alfred Sisley. The last opening, was at Het Arendsmanhuis. It was the opening of the exhibitions Charlotte and Emily Salvia by Linsey Kuijpers.

Saturday, September 28, 2019

FPGA course

I joined the FPGA course at TkkrLab organized as part of the bimonthly CyperSaturdays. The course was developed and given by Paul Honig from RevSpace and is based on the UPDuino v2.0 sold by Gnarly Gey. The course started with the elementary priciples. During the course, we mostly focussed on programming the (very bright) RGB-led on the board, but sources for reading the digital temperature sensor (DS18B20) are included.

Allée Rentrée

In the evening, I went to Allée Rentrée festival with art and music. He liked the following:
  • FE 26 by David Scheidler
  • Electric Guitar Paintball Sniper by Ole Nieling
  • Devotie by Erik Kok
  • Paintings by Bas van der Linde.

Tuesday, September 24, 2019

Flap Flap

I went to see the Flap Flap installation by Philip Vermeulen at the University of Twente. I was a little late for one of the performance, so, I only watched the last third of it. I did not have time to wait for the next performance.

Monday, September 23, 2019

Walking at Night in NYC

I watched the Walking in Heavy Thunderstorm at Night in NYC video and tried to figure out the route the maker took. I discovered that there are six segments in the video (and a very short one, that I do not count). With Google Earth I made a KML file of the routes of each segment. It seems if the maker made two walks starting from East 34th Street and Park Ave, and that he alternated the segments from these walks, one in order and the other out of order.

Sunday, September 22, 2019


It felt like spring today. At the end of the afternoon, it was much warmer outside then inside. Temperatures reachted 26.6°C at weather station at Twente Airport. The garden looks very green again compared to a few months ago. It seems that the leaves of the small chestnut tree have withered. I hope it has not died. I tried to water it through the summer when it was dry, but I might have forgotten it.

Friday, September 20, 2019

Dead end?

With the results of last Sunday, I tried to find the 35 constant weight vectors for A(11,4,4) as mentioned in a table. I did this by starting with the 54718 solutions consisting of 19 vectors and try to extend it further. The program found 46080 solutions (possibly containing doubles and missing some) consisting of 30 vectors and non with more than 30 vectors. It looks like a dead-end. Which actually does not surprise me, because requiring that 18 vectors will be close to one vector, might force them to be spread apart too far and in a some what regular manner, that no space is left over to select the remaining sixteen vectors from.

Thursday, September 19, 2019


Tuesday, September 17, 2019


Sunday, September 15, 2019

54718 solutions

I continued working on the program to calculate the number of different solutions of 18 constant weigh vectors 'around' a vector with seven ones and four zeros, where around means at a Haming distances of four and such that all vectors are at distance of at least four. The program found 54718 different solutions taking in consideration all possible permutations of the 'rows' of the vectors.

Saturday, September 14, 2019


I went to Tetem art space to look at the exhibition Xenobodies in Mutation. At the Exploring-Lab some people were assembling a small motor powered by solar cells. I also joined and assembled one.

Wednesday, September 11, 2019


I recieved the book Kilo-Girls written by Julia Luteijn in English, which I bought from the author for € 13.90 (including postages).

Tuesday, September 10, 2019

1773 constellation

I continued working on the 18 vectors problem (which is related to the KABK wrapping paper) and this evening, I worked on a program to calculate the number of unique ways the octahedron can be tilled with the 19 patterns I found on September 1. I arrived at a program which calculates in how many ways the edges can be marked with on of the three possible patterns, such that they are compatible with the 19 patterns. Such a 'constellation' does not neccessary match a solution of the patterns and even if it does, there could more than one. The program found 1773 such constellations. When at home, I thought about a different approach for finding the solutions for the 18 vectors problem.

Friday, September 6, 2019


I was a guard at the former VVV-building. The first half on the second floor and the second half on the third floor. These floors had all the Young Blood nominees, selected from the graduates of the various art academics in the Netherlands. I found the following nominees mentionable (roughly in the order I encountered them at the exhibition):

The building also had the projects by the freshman students of the Creative Technology major of the University of Twente. I used the Embry-o-'matic to 'create' a designer embryo from Stork Industries. Mine was #10293 and I had to 'pay' $4929. In the evening, I again, helped out at the Oude Kerk, because some volunteers wanted to have dinner and one did not show up (or left early).

Thursday, September 5, 2019

Rainbow at Gogbot

While waiting with some other volunteers for the introduction tour along all the locations of the Gogbot festival, we saw a rather bright, double, and complete (as far as I could see) rainbow. I took several pictures, one of which is shown to the right. After the opening, at eight, I helped out as a guard in the Grote Kerk because there were a lot of visitors. I stood near the entrance, close to The Mictobial Vending Machine by Emma van de Leest, one of the few artist being present at the exhibition in this location and explaining her project to visitors. Also close were the Pink Chicken Project, Al¿ve, and Caravel. There was not much interaction or moving projects as in some of the previous years and several vistors commented about this to me while leaving the venue. At eleven, after the exhibition closed, I went to the Metropool concert room to have a peek at the Gogbot lift off // Experimental Electronics & Modular Night, which was free for volunteers, only to discover that they had very strict rules with respect to bags and coats, and that the small lockers costed two Euro each. I was a little disappointed, because I had hoped to work a little on my notebook while listening to the music, and decided to go home.

Wednesday, September 4, 2019


Today, my mother became a great-grandmother, because the oldest son of my youngest sister became a father. It also means that I have become a granduncle.


Sunday, September 1, 2019

18 vectors

Yesterday, while guarding the entrance for the retro game day, I looked at the problem of finding at the 35 vectors. I have been looking at finding collections of eighteen vectors at the Haming distance of four from a vector. The reason why there are eighteen is because there are only six ways to change two of the four zeros into ones and at most three non-overlapping pairs of ones that are changed into zeroes. I realized that there are some restrictions as to how for three patterns of zeros that are changed into ones that only differ at two locations, such as for example, 1100, 1010, and 0110, the way the ones are changed into zeros must all be different. Because if they are the same, the Haming distance is only two. I got the idea that there were only four configurations, not counting all kinds of symmetries. But when I was at home, I wrote a program, which produced 19 solutions. Which meant that either I was wrong or the program. Today, I wrote the following animation to display the 19 solutions. The three colours refer to the three ways in which zeros are changed into ones and the three lines refer to the patterns in which the ones are changed into zeros. Any of the 21 possible lines cannot have two colours and there cannot be a point where to lines of the same colour meet.

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

In the evening, I realized how there eight combinations of three vectors, such as in the example, and that these can be visualized as the triangles of the octahedron. And also that each edge represents the lines of two colours and that there are only three possible patterns of these, namely, where the lines are a cycle of six lines, a cycle of four lines and a path of two lines, or a path of six lines. This put a lot of restrictions on how the various patterns can be placed on the octohedron, and that that is a good way to determine all unique (with respect to symmetries) combinations of 18 vectors there are.

Saturday, August 31, 2019

Retro gaming day

I helped out at the retrogaming day at TkkrLab.

Thursday, August 29, 2019


Today, the heatwave, which started on August 22 (locally) and on August 23 (nation wide), has been terminated. It was the 28th national heatwave on record. Last night there were thunderstorms and some heavy showers. Today, the temperature reached 24.5°C. The maximum temperatures in the past days (at the Twente Airport weather stations) were: 25.8°C (22), 26.6°C (23), 30.0°C (24), 31.1°C (25), 32.6°C (26), 33.3°C (27), and 30.9°C (28).

Tuesday, August 27, 2019


Tonight at TkkrLab, I received two badges: the CampZone 2019 badge and the card10 badge from the CCCamp 2019. I made some donations to the Badge Team for both of them. The second is not really a badge, but a smart watch with a Cortex-M4F core.

Tuesday, August 22, 2019


I went to Amsterdam. At 13:40, I bought the following two books from bookshop Scheltema:
  • The Little Review "Ulysses", written by James Joyce, edited by Mark Gaipa, Sean Latham, and Robert Scholes, written in English, published by Yale University Press in 2015, ISBN:9780300181777, for € 12.50.
  • 2001: A Space Odyssey written by Arthur C. Clarke in English and published by Orbit in 2018, ISBN:9780751573756, for € 5.95
I went to gallery Ron Mandos to see the exhibition Best of Graduates 2019. I was a little disappointed about the choice of the works. I did not see many that I remembered having seen at the various graduation exhibitions that I attended. I did like the following: Afterwards, while walking back to the train station, I also came along Casa Luna Studio with the exhihibition Intersections with works by Frans Horbach. On the way home, I stopped in Utrecht and visited the bookshops Steven Sterk and Broese.

Monday, August 19, 2019


October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
Alzheimer's Disease
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