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Additive noise

Whenever you measure something you usually repeat these measurements, in order to determine not only the quantity you are looking for but also access its uncertainty. Given that you have measured different quantities and derive a new one from a set of these, one will use these formal errors to weight the impact of these quantities. A simple example would be this:

Three groups measure a length together with its formal error. If someone wants to get the average over all three groups, he would compute a weighted mean (based on the formal errors of each group) as a most reliable solution. The problem is only that the information on how the formal errors are computed is not preserved. E.g. one group could compute the standard deviation of their measurements from only three observations during a time when systematic effects were small, but the other groups had much more data to get their results and thus see a larger formal error coming from systematics. However, the results based on the three measurements will get a much higher weight in the combined solution although it is basically less valuable than the other two results.

In order to compensate for such effects one can add a certain amount of uncertainty, i.e.

I am going to demonstrate this by a quite illustrative example. I took four randomly distributed 2D points and then computed the weighted mean of all points by applying formal errors which I took from a normal distribution generator (with zero mean, and a standard deviation of one). I.e.

For each Monte-Carlo run I computed 300,000 points and I changed the additive noise level between 0 and 2 for each run. Here is a small animation looping through the different noise levels.

For low additive noise the points tend to be inside the area spanned by the four points (if you look at the density plot on the right you see that it is slightly more likely that a point is on one of the diagonals than on another place). However if you start adding noise, the original data weights become less important and the point are coming closer to the “truth”, i.e. the unweighted average of all four points.
This small post does not show anything surprisingly new, but I think it demonstrates quite clearly how one can “tune” a solution based on different data weights into totally different states.

Popularity: 1%

Posted in math, programming

Spicy recommendation XVII

This time I am going to present another Indian(?) restaurant in Higashi-Murayama area. The restaurant is named “NAANBAGAN”, whereas the owner has added “Indian curry and Naan house” to the title as well. The restaurant does not have its own homepage, so one needs to rely on e.g. this tablelog information. The place is located close to Kumegawa-station and should not be to difficult to find for someone who checked the map before. When entering the restaurant the staff was not really motivated to offer a table (although there were plenty of empty ones) and there is a sign on the table that warns (!!) you that if one person takes a set-menu but the second one goes for a single dish only, the second one has to pay extra for each Naan he/she orders. Basically, each of the sets comes with soup, salad one curry, Naan or rice (Naan comes as all-you-can eat) and a drink. I had mango lassi, which was more like a cup of ice-cubes with little milk and a mango syrup. The Naan is difficult to eat as it is coated totally with butter and although quite thin it is not very crispy. Curries are below average and the starters (salad and soup) seem to be ready-made or at least prepared the night before. And now about the spice: One can order only three spice levels, starting from medium (the menu does not list mild or sweet, which is a little bit strange). I had an extra hot keema-curry, which was very soupy and the spice level was not very pleasant as most of is was covered totally by the oily taste of the dish. So overall it wasn’t a very pleasant experience, although the price of only 750 Yen makes it a good alternative to Mc Donalds which is closer to the station. However, for those who want some good curry its not really a recommendation.

My rating: ★☆☆☆☆☆☆☆

Popularity: 1%

Posted in Drink, Food, Spicy recommendation

Unruly passengers


An unruly passenger on a plane can be somebody between just drunk and a little bit nasty and a highly dangerous terrorist who poses a real threat for the safety of the people on board and on the ground. It seems that are a few cases when airlines over-react, but in most of the situations the cabin crew had to deal with total idiots who attacked the staff or other passengers. Who thinks that an “unruly passenger” is a rare case, is wrong. Just have a look on The Aviation Herald and enter the word “unruly” in the search field on the top. You can see that almost every 2nd or 3rd day an idiot thinks he does not need to follow FAA rules (or basic manners) and is being removed from a plane. That’s OK if it happens before the flight departs, but if the passenger gets “unruly” during the flight, the plane needs to touch down and then delays are the logic consequence for all passengers. Until now I did not have an “unruly” passenger on my flight, except some guys who used to snore like a motor saw. But unfortunately FAA rules do not support hand-cuffing and escorting such nasty passengers from the plane :-)

Popularity: 1%

Posted in travel

Spray-on antennas

It may sound like utopia, but Chamtech Operations presented their new nanotechnology-based spray-on antenna technology at Google’s Solve for X forum. This idea is that one sprays the material on any kind of surface and the nanotech particles turn into an active antenna. According to the presenter, trees, poles or any other object which is already outside in the environment can be used to apply this technology. Sounds very futuristic, but if it works as announced it would enable quite a large variety of new applications.

Popularity: 1%

Posted in Uncategorized

Two-line elements of current GLONASS satellites

The Celestrak page provides a variety of two-line elements (TLE) for different satellites, including orbit information for navigation satellite systems like the Russian GLONASS. Unfortunately, there are more satellites listed in the TLE data-set than are currently operational. E.g. today (Feb 15, 2012) there are TLE data-sets for 31 satellites but the official GLONASS page lists only 24 SVs operational. Since I need to track only those which are really transmitting signals I wrote a quick and dirty shell script that downloads and extracts only those TLE which are really relevant for real-time signal tracking. Please feel free to use the following few lines of Bash/Awk if they are of any use for you:

#!/bin/bash
#get the current GLONASS constellation
wget http://www.glonass-ianc.rsa.ru/en/CUSGLONASS/getCUSMessage.php
awk '{if(index($1,"|")>0 && $14=="operating"){print "COSMOS " $4 " (" $2 ")"}}' getCUSMessage.php > operational.glonass
#download the TLE of all GLONASS satellites
wget http://celestrak.com/NORAD/elements/glo-ops.txt
#extract only the operational ones
while read line
do
grep "$line" glo-ops.txt -A 2 >> glonass.TLE
done < operational.glonass
rm getCUSMessage.php
rm glo-ops.txt
rm operational.glonass

Popularity: 1%

Posted in computer, GPS, programming

Milk vending machines in Japan

Soft drink vending machines are something that belongs to Japan like burger to the US. In most of the cities you can find such vending machines within a distance of less than 200 m independently where you are. Although the density of these machines decreases once you go to the country side, there are still millions (see Wikipedia here) out there waiting to serve thirsty customers. Most of these machines are equipped with water bottles, soft-drinks and beer. A few machines operated by local companies are filled with small milk packs, but this seems to be quite labour intensive as one needs to make sure that all the milk product are available to the costumer before the expiration date has passed. I am aware of only one type of location where enough milk-thirsty costumers are passing by in order to be worth for the company to stuff the machine with fresh products: Onsen. At such locations people are thirsty when they finish their hot bath or escape from the sauna and they can select among a variety of soft-drink vending machines including at least one machine selling milk products. I have to confess that I am also one of those customers who buy one or two bottles of milk after finishing my bath/sauna. I really enjoy the fresh taste, and one can select between a variety of milk products which are usually not sold in supermarket and convenience stores. And the price of 100 Yen (1 EUR) is nothing that really hurts my wallet, nor does it make me feel guilty of drinking some junk soft drink that contains mainly sugar.

Popularity: 1%

Posted in Drink, Japanese

The “broken link checker” for WordPress

Yesterday I added a very useful plug-in for this WordPress installation – the broken link checker. Once it is installed it searches all links in posts, pages, etc. and checks if they are still valid. By this nice little tool I found out that 50 of my ~950 links which I mostly had in my posts were no longer valid. Thus, I am now editing all those posts in order to make sure that visitors of my pages are only provided with correct links. I hope hope to have all the entries fixed until the weekend.

Popularity: 1%

Posted in computer, programming

Japanese school building architecture

Almost all public schools in Japan have one thing in common – they look very similar. There is not much difference in the way how the building looks from outside, independently if it is an elementary school, a junior high school or a high school. It seems that decades ago some guys (likely not architects :-) ) agreed on a certain “design” which has been realized across the country. Thereby the typical school building consists of a cubical center building which host all the class rooms. This main building is usually close to the sports field, around which other facilities (like pools, sport halls, etc.) are arranged. The interesting thing is that the cubical class room building is always built with concrete and has large glass sliding windows, independently if the school is located in a hot place like Okinawa or if the location is in Hokkaido with very cold and long winters. For someone living longer in Japan these school buildings belong to the landscape. I think these buildings are very functional and have served generations of pupils. Although those schools which were built 30+ years ago look really shabby from outside, they are still serving their purpose (maybe a better insulation would be good for saving energy!). However, it is nice to see that the government has started to rethink the way how public schools should look like. Newly built schools seem to be really designed individually giving the location a somewhat unique feature.

Popularity: 1%

Posted in Japanese

Onsen manners

Last weekend when I went to a nearby Onsen I had a look at the poster which explains all the things one should not do when visiting such a place. Since saunas have recently become popular, many of the typical onsen locations are now equipped with saunas as well so the poster also includes rules about how to behave there. In order to make sure that the few foreigner who visit such a place behave well the poster explains those rules also in other languages for those who are not able to read Japanese. So here is what the Japanese poster tells you (I hope that my own translation is correct :-) )

  1. Wash yourself before entering the onsen tub!
  2. Make sure that your hair does not get into the water!
  3. Make sure that your hair does not get into the water!
  4. Wash before entering the sauna and rinse the sweat before entering the onsen tub!
  5. Parents should watch their children and not let them play!
  6. You should not bring your towel with you into the onsen tub!
  7. Rest at locations where you don’t bother anyone!
  8. Take care of other when being in the onsen tub!
  9. Don’t wash yourself in the onsen tub!
  10. After using any tools, put them back from you go took them!
  11. Don’t spray the shower on somebody else when cleaning yourself!
  12. Don’t leaf anything behind at the shower place or onsen tub!
  13. Don’t spit and don’t let your kids pee!
  14. Don’t leave the shower running after you are finished!
  15. Wipe and dry your body when entering the changing room or sauna!
  16. Don’t talk with loud voice!
  17. Only bring towels and bath tools to the designated area! Don’t wash your clothes!
  18. Enter the bathroom and onsen tubs naked (no swimsuits)!
  19. Respect other people!
  20. Don’t enter the tubs when you feel ill or are drunk!
  21. Don’t bring cameras and hand phone and don’t take pictures!

Of course I obey these rules and I hardly see somebody who does anything strange in the onsen area (except a few tourists who go to such a place for the first time :-) ). However, a few Japanese seem to ignore rule (7) and take a rest wherever they want. Even if the area is crowded those people lie on the edge of the onsen or on other unpleasant locations. But as other guest also feel bothered by them it usually does not take long until someone claims to such a guy. He then apologizes, takes his towel and moves to a less disturbing place. Rule (15) seems to be ignored by more than half of the Japanese people who enter the sauna. It says clearly that one should dry his body before entering the hot room. I think this rules has been set not only to make sure that someone does not bring too much water (which evaporates and increases the humidity) to the sauna but mainly to allow the human body to start sweating naturally. Last time I even saw a guy who spent 5 minutes in the sauna, then went to the pool with cold water for 3 minutes, came back to the sauna for 5 minutes, … and so on. He did this for almost 2 hours. I am not sure what the purpose of this “exercise” was, but his body might not have liked it much.

Popularity: 1%

Posted in Japanese

Cops not allows wearing NYPD gear after work

The New York Police Department (NYPD) is not only Americas biggest police force, but it is maybe the one that is most known around the globe. And since the department has gained national and international fame and popularity, a variety of official and less official NYPD goods are sold in New York city and many other places (I have seen such good even here in Japan). Best sellers include caps, jackets and other wear which has the famous logo being printed on those products. Thus it happened that even real NYPD cops had such items at home and wore them in their leisure time. For some unknown reason, some people did not like this idea and issued an order on January this year, stating the every cop has to refrain from

… wearing any item of apparel which contains a department logo or shield or in any way identifies wearer with the New York City Police Department unless approved by the Uniform and Equipment Review Committee prior to being worn by a member of the service, uniformed or civilian, on or off duty…

This is not only restricted to caps, T-shirts and other fashion but also to mugs and other goodies which have the NYPD logo being printed on. For me it does not make sense why the cops are not allows to wear such things, which everybody else (even criminals) can legally purchase at any store and use r whenever he or she wants. I am not aware of any other police force that has such a rule and in most other cases cops are quite proud to wear the tourist gear even after work. BTW, I think that even Japanese policemen are still allowed to buy models of their cop cars :-)

Popularity: 1%

Posted in Japanese, Uncategorized
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