JabRef

A quite nice .bib document organizer.
It makes me comfortable to write down my comments to every paper I read.

Power sum

sum(i) = n(n+1)/2
sum(i^2) = n(n+1)(2n+1)/6
sum(i^3) = n^4/4 + n^3/2 + n^2/2
...

A site contains optimization online resource

When I check the statistics for COR@L today
I get the following link, which provide some good online resource for optimization.
http://plato.asu.edu/sub/tutorials.html

The 3rd weekly report

This week, I work for 56 hours. Due to easier homework of Graph and Network, I only spent 28.5 hours in study. Also I make a little progress on one of my research project.

Beside work, I watch the football game between Lehigh and Princeton. I sit too low so that sometimes I cannot clearly catch what was going on in the field. Next time I will sit high enough.

I also watch the film The Illusionist. It is a wonderful movie. Originally I think I would fall in sleep during the movie. But I cannot stop enjoying it and have no chance to have a nap.

(-1)^(1/3)=0.5000 + 0.8660i ?

This time, I meet another problem about math operation in software.
In matlab, when you try
(-1)^(1/3)
What result do we get. It is not -1 but 0.5000 + 0.8660i
You need to use nthroot(-1,3) to get -1.

This time, excel gives me the answer I want.

I am so frustrated now. This time I use more than 4 hours to debug my program which contains similar operations in my matlab code.

Do I know too little about basic math or Matlab provides too much.

My 2nd weekly report

This week, my course work increase 1 hour. It seems that 30 hours per week is average workload 4 courses taught all by professors from math department. They usually have more homework than IE courses. But it is worth doing that.

But research work drops to 23 hours per week. That's because I finish all the coding work for one of my project. I need to increase it to above 25 hours a week.

Also I have played tennis twice this week. I am still seeking the feeling about backhand, which I lost for a month after I changed my habit and cannot go back.

EXCEL vs GOOGLE

When I try to verify the correctness of a sequence. I need to compute the following fomula

=-1*((0.4^4-3*(0.4^3)+0.4^2)*10+(0.4^3-2*(0.4^2))*15+(0.4^2-0.4)*20+0.4*25+30)+100*(0.4^4-2*(0.4^3)+1)+50*(-0.4^4+2*(0.4^3))

Excel gives 66.144. I takes me more an hour to debug. Finally I find it is not my fault

But google gives 63.58400

Actually google gives the correct result.

How can I trust excel anymore?

I still remember two year before Excel can generate negative number from [0,1] random variable. Luckly I get the patch to fix it. This time, I don't how I should do.

chalk and slide

This semesters, all my attended courses are taught from Math department. Those professors like to present their material by chalk on the blackboard. In contrast, most of my IE courses are taught through slides. But I have to say that I love chalk style. You can see how the professor thinks from chalk but not from slides. Also when you take down the notes, you not only use ears to listen, but also use eyes to look and hand to write down. The more 'sensors' you use during the class, the more and the longer you can remember.

One possible reason for the IE professors to use slides more than chalks is because IE professors uses more computer than Math professors. So the technology not always create better way to learn. But slides is healthy way to teach since the more chalk you use, the more chalk ash you absorb. Also use slides may have huge scale of economic. If let me choose which way I use. I would be half and half. Just like last semester nonlinear programming class. Use the slides to show main ideas, use chalks to show the details.

My 1st weekly timesheet

Although, it isn't 5:00pm at Sep. 3, I like to post my 1st weekly timesheet. The total hours on study are 29.5 and on research are 31. I am quite satisfied with my work in the 1st week. I will go on this self monitor mechanism

Andre Agassi & NP-complete

I just finished watching a unbelievable tennis game. No match can be better than this one. All the unbelievalbe games have equivalent elements, like all NP-complete problems are equivalent.