Sunday, February 25, 2007
Now I know why going downtown takes so long -vwv

Before the days of the NEL, there used to be a bus that travels from my place to City Hall. Nowadays, I take a bus to Serangoon MRT and take the train to City Hall. Sometimes, it's really fast. But on other times, I can't help but feel it's taking really long. I never gave it much thought until recently when I suddenly realized I was looking at the average traveling time and that's the problem.

The important thing is not so much the mean traveling time but the standard deviation, which is the measure how precise the mean traveling time is. With a small standard deviation, you'll almost always take about the same time to travel downtown. With a large standard deviation, you'll usually be very late or very early. The thing about the standard deviation is, it always adds up.

In the old days when I can take a bus downtown, the mean time is
40 min bus ride
+ 5 min waiting
= 45 min.
The standard deviation for the bus wait is perhaps about 2 min.

Now when I go downtown, the mean time is
5 min bus ride to Serangoon MRT
+ 10 min bus waiting
+ 10 min train ride to Dhoby Ghaut
+ 4 min train waiting
+ 3 min walk to North-South line
+ 3 min train ride to City Hall
+ 2 min train wait
= 37 min.
An approximate 8 min improvement. Nice.
But what about the standard deviation? It is
2.5 min bus waiting
+ 1.5 min train waiting
+ 1 min train waiting
= 5 min.

Assuming that more than 80% of the time, we arrive within plus minus 1.5 standard deviations of the mean time. The implication is this:

For more than 80% of the time,
the old route will take between 42 to 48 min.
The new route will take between 29.5 to 44.5 min.

So if I want to arrive on time for the worst-case scenario, I can leave the house a pathetic 3 minutes later than before but there's a very high chance I'll arrive too early and waste my time waiting for people.

Or if I'm really optimistic and assume minimal waiting for all the buses and trains, I can leave the house an impressive 12.5 minutes later than before but there's also a high chance I might end up very late and waste other people's time.

But since I'm more of the former, no wonder I don't feel like I'm getting much benefit from being forced to take the NEL. Not to mention I can no longer sleep on the bus throughout the trip.

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Yiheng made 1:04 PM

3 Comments:

I agree. That's why I prefer a direct, long bus journey than taking trains.
By  bOb™, at 6:04 PM  

Our current transport model inclined towards the hub-and-spoke model, so you can expect there to be more transits. Having a monopoly on transport in Singapore doesn't help either.

What might be interesting to do is to setup (us) a competing SME-ish transport company. Ask users to register with us their location and typically travelling time and costs...and we will undercut SBS/SMRT with our competitive services. Think Priceline + Tiger airlines combined. Basically just destroying the hub-spoke network and addressing the market inefficiences by optimizing travelling routes for our group of customers.

-Lower cost.
-Get to where you need to go quicker and less waiting.
Not a bad idea huh?
By  Soqcrates, at 6:57 PM  

Good idea. Since it's a small scale business, we can just whack SBS/SMRT on routes where they are the weakest, i.e. require multiple transits.
By  Anonymous, at 7:27 PM  

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Tuesday, February 20, 2007
Androids -vwv

A few weeks ago, I was watching a show on TV where a guy was explaining research into how humans react to androids (humanoid robots) that look like real people. He said that while one would not usually care if he kicks a robot that resembles a box with wheels, people would get upset if he were to hit a robot that looks a lot like a human being even if the robot is equally robust.

I never really thought about this before but it does seem kind of true. I'm quite sure I wouldn't care if someone slaps C3PO and I wouldn't mind giving R2D2 a kick myself. But I think I would feel kinda bad if someone kicks her (see picture) in the face.



This is Repliee Q2, an android designed to look and have subtle facial movements like humans. It looks a little creepy up close (I think she doesn't blink often enough) but from a distance, it's pretty realistic. Her movements are a little jerky because they used pneumatic actuators rather than electric motors.

Here's a video clip. Embedding is disabled so you'll have to click on the link. Here's the site at Osaka University. There are more video clips and explanations.

If she can move like these robots, it'll be awesome. If only I could borrow one of them to take part in the TechX Challenge and win a million bucks.


Here's another video about the Repliee android, not sure whether this is Q1 or Q2.

Link to YouTube clip
It's rather amusing when you read the comments and find things like "I'd have sex with it". And to think they used to call the iMac sexy. I guess if there are people who find a rounded plastic shell containing a bunch of circuits sexually appealing...well. Personally, I think the doctoral student in the video is way cuter than the android. Then again, they look so similar, Noma might actually be Repliee Q3 in testing phase, who knows.

-- permalink --
Yiheng made 6:51 PM

2 Comments:

FREAKY!!! They look so real....

I want one too, without the clothes.

But yeah, I think Chii totally pawns her ass.
By  Soqcrates, at 10:08 PM  

very creepy....
By  Masato, at 4:48 PM  

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Saturday, February 17, 2007
See ancient Chinese artefacts for free -vwv

Not say I know good stuff dun share arh, entrance to Asian Civilizations Museum is free on Monday. Go see these 3200 year-old bronze age stuff at the Mystery Men exhibition. My history is a little hazy but I think these items are from a period even earlier than the events of 封神演義 (Investiture of the Gods), which make them older than some Chinese deities.

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Yiheng made 6:07 PM

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Friday, February 16, 2007
When the Sun turns Black and the Moon turns Red -vwv vww

Eclipses. The only time when the Sun is black, kind of, and the Moon is red. In anticipation of the Total Lunar Eclipse of 4th March 2007 (3rd March for North America), I was discussing eclipses with Shuquan when he suggested we go eclipse-chasing in China for the Total Solar Eclipse of 2009. So I searched the web and found these two interesting maps of solar eclipses from 2001 to 2025.




The blue regions are areas that can see the total solar eclipses while the red regions are regions that see the annular solar eclipses. Annular solar eclipses occur when the Moon moves in front of the Sun, but is too small to cover the entire disc. So if you happen to be looking at the Sun, you see a ring of very very bright light. Otherwise, you won't really notice anything. Personally, I think total solar eclipses are more exciting. In this case, the Moon covers the entire Sun disc. Day turns into night instantly, stars appear, temperature drops and supposedly animals become nervous and dogs bark like crazy. This is what I'd like to see in 2009 when I go to China.

By the way, if you are wondering why we don't see solar eclipses very often, notice that most of the regions are over the oceans, so it's just too bad. Besides, not everyone is rich enough to go chase after every eclipse.

In the meantime, I am really looking forward to the total lunar eclipse on the morning of 4th March. For the past few lunar eclipses that I have seen, the Moon just turned black, being in Earth's shadow. But sometimes, long wavelength light (basically red light) gets bent in Earth's atmosphere and manage to reach the Moon during the eclipse. That when you get a red Moon, which is what I'm hoping for in March.

If you are interested, here are the details. There's another one in August if you miss the one in March. Time given is Singapore local time. For the benefit of those who didn't know, the Moon rises in the east and sets in the west.

Total Lunar Eclipse, 4 March 2007

Circumstances of the eclipse
Moon entering penumbra 0416 h
Moon entering umbra 0530 h
Middle of eclipse 0721 h
Moon Set 0759 h

Total Lunar Eclipse, 28 August 2007

Circumstances of the eclipse
Beginning of eclipse 1552 h
Middle of eclipse 1837 h
Moon rise 1914 h
Moon leaving umbra 1923 h
Moon leaving penumbra 2024 h
End of eclipse 2123 h

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Yiheng made 11:13 AM

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Tuesday, February 13, 2007
The Timeless Problem of Fair Division -vvw vvx

I usually avoid putting mathematics-related posts here but I think this one might interest some people who usually find math distasteful.

Here's an interesting article I came across some weeks ago.

Sharing Your Cake--and Eating it, Too

It's about the age old problem of sharing a piece of resource, e.g. cake, fairly between two or more parties. For the simpler version of two parties, the traditional solution of "you cut, I choose" works quite well. Except what if the cake is half chocolate and half strawberry, and person A hates chocolate while person B has no preference over either flavours? You might end up having one or more person feeling he got ripped off even though he did physically receive half a cake. The article talks about some guys who came up with a procedure that ensures each guy feels as though he gets at least half the cake.

Actually, it seems like the method was not really about fair division but rather, about dividing in such a way that nobody feels cheated. In my terms, I would say it depends on the individual's assigned utility on each part of the cake (assuming it's not homogeneous). In fact, I think it's trivial (my word for bloody obvious) that people assign different utility to different things. While optimization may not be a simple matter, to improve from simple physically equal division to a more optimal division (with equal or greater utility for each individual) should be quite easy.

Unfortunately, the property of obviousness is subjective. This is where I shall complain, like all Singaporeans do, about the stupidity of some systems, in this case, assigned duties in NS. Somehow, people have the idea that it is good and fair to divide duties such that everyone has the same proportion of guard duties and COS duties. This is retarded, just like in the cake cutting problem. Perhaps someone loves doing guard duties and another loves doing COS. It seems pretty obvious that a swap is one step towards the optimum but nooooooooooo. No wonder they say "military intelligence" is an oxymoron.

-- permalink --
Yiheng made 10:06 PM

1 Comments:

Hey! I once deliberated this concept of assigning duties in the army before. It works like SP or EP in which the people in the roster submit their disutilities/utilities in doing COS and guard duty anonymously, then impartially allocate duties ensuring maximum utility for everyone.

But I submit to you 2 problems in why this wouldn't work out in the army, other than the 'military intelligence part' One aspect is that the disutility of duty is dependant not just on personal preferences but our inevitable comparison with the disutilities of others. I mean, 2 COS duties won't seem too bad at first, but you do feel shittier if most of your friends are getting lesser. People still tend to be stuck in the quantity over quality mindset.

I can almost imagine Royston kao-pehing why he has two COS duties when Celester only has 1 thursday guard duty, yet if you ask him if he wants to swap, he would refuse.

Second is the fact that most people can't comprehend this exercise of assigning utility. Let alone people from the army. They might potentially see it as a system we cleverly devised for the scholars to somehow benefit from.

let's face it: People who aren't inducted in this still remain as terrible decision makers.
By  Soqcrates, at 11:28 PM  

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Saturday, February 10, 2007
Singapore is here to amuse me -vwv

(Chinatown MRT)
Why is the old woman who shoved everyone out of her way to be the first to alight the train also the same woman who created a traffic jam on the escalator?

(Raffles City)
Why does the woman who sells combs have messy hair?

(CD shop at Capitol)
Sales assistant saying loudly, "You want to buy Taufik?!" followed by laughter all around.

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Yiheng made 9:42 PM

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Monday, February 05, 2007
Weekend Activities: SSC and SSO -vvv vvz

I visited the Singapore Science Centre with Shuquan on Saturday, 3rd Feb. You can read all about that here. I haven't been there for more than a decade but it didn't really change much. Considering that children are getting smarter with each generation, the Science Centre's target audience must be getting younger and younger. They're still displaying Bohr's model of the atom. I would think lower secondary school children should be able to understand the quantum mechanical model by now. Well, at least they were up to date on the status of Pluto not being a planet any more. An amusing find was the old hand-crank field telephone that I was taught to use in School of Signals back then is now an exhibit in the Science Centre.

On Sunday, I went to a chamber music concert. I don't usually listen to chamber music but it's been a long time since I last went to a classical music concert. Ah, those were the days when I could get cheap tickets to Toronto Symphony Orchestra performances and the concert hall was just walking distance from my house. Anyway, I gladly accepted Shimin's invitation to watch the VCH Chamber Series performance Slavic Expressions with her, Xiaojing and Yun Qin. Part of the reason was my interest in music with nationalistic themes and folk colours.



Embarassed to say, I doubt I can identify Slavic music if I ever hear it again. The first piece was Capriccio for piano left hand and chamber ensemble. Technically difficult no doubt but I found it quite hard to digest. The abrupt mid-phrase breaks, which was supposed to build suspense, made me feel like I was being thrown out of my seat when the bus driver stops the bus suddenly at a traffic light. Moreover, my ears weren't very used to amodal music. Fortunately, the second piece, Dvorak's popular Piano trio in E minor, Op. 90 "Dumky" performed by the Feng Trio, was less demanding on the ear. Otherwise, I would have left the concert hall a very confused man.

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Yiheng made 9:47 PM

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