# Michael Zhang

## Archive for March, 2006

### 急了,

Monday, March 27th, 2006 -- By Jade

### 快到清明了

Saturday, March 25th, 2006 -- By Jade

### 孙悟空

Saturday, March 25th, 2006 -- By Jade

### 老公的决定

Saturday, March 25th, 2006 -- By Jade

### Big Decision

Friday, March 24th, 2006 -- By ET

After spending 6 years at MIT. I decided to commit a major change in my life, I took the offer from HKUST (Hong Kong University of Science and Technology). That means, we are moving back to Asia, and it will be in the near future.

The job market was funny, I may write a longer piece later since I can’t really describe how much I experienced here. The IT market has not been any better than the previous years after the Internet bubble burst, as a consequence, there are only less than 10 openings in the so-called research institutions, which are generally considered to be better than "teaching institutions" since professors in research institutions have less burden of teaching and can do more creative things in research. The number of job candidates goes beyond 200 people. That means a lot of potentially creative people who might be great researchers will end up in teaching institutions and be burdened with 6 courses to teach a week. Some may just go to the industry and never will be able to use some of what they have learned to be a researcher.

I guess some people need to thank me since I gave up a few nice offers here in the US. I like these schools very much (again, this warrants a longer blog entry, I made some really good friends from these campus visits), but I can only take one offer and my optimization problem is a constrained one with factors about my wife, children, our parents, our friends, our career plans, etc… HKUST turned out to be the best option for me.

I’m eager to write about the great things about HKUST now, I may write a longer piece later with more details

research support

1. it is comparable to top 10-20 US business school’s support
2. as a consequence, it is not surprising that just by counting the number of top business journal publications, it ranked about 20 among US schools

strong faculty profile

1. I was surprised to find that the majority of the faculty members are affiliated with very good business schools
2. the dean got his PhD in U Chicago, the head of my department came from Stanford, … …

amazing history

1. HKUST started in the early ninties, within 15 years, it has accomplished to be a major research institute in Asia
2. it really sets a good example for how to build a good school, I know other universities in Hong Kong are strongly influenced by this
3. there is a book written by the first president of HKUST about the history, I heard many good things about the book, looking forward to read it

gorgeous campus

1. My friend Gordon Gao named it "the best campus in Asia"
2. it has ocean view and mountain view, you can not be not productive with these :-p

Since I’m working on my thesis now and have to defend my thesis on May 1st, I really don’t have time to notify all my friends about this decision. Hope this entry can serve as an announcement to let you know about my future whereabouts. If you are in Asia, we are much more closer, and if you are in the US, don’t worry, I’ll be back at least twice a year, plenty of chances to hang out together!

### 进步了

Wednesday, March 22nd, 2006 -- By Jade

### 忙

Wednesday, March 22nd, 2006 -- By Jade

### Gini Coefficient

Tuesday, March 21st, 2006 -- By ET

The Gini coefficient is a measure of inequality. It is usually used to measure income inequality, but can be used to measure any form of uneven distribution. It is closely related to Lorenz Curve

(figure courtesy to WikiPedia)

I usually use perl to manipulate my datasets, and I could not find a procedure to calculate gini coefficient in perl. So I wrote one.

The definition of Gini coefficient is:

but,The Gini coefficient is often calculated with the more practical Brown Formula shown below:

$G = | 1 - \sum_{k=1}^{n} (X_{k} - X_{k-1}) (Y_{k} + Y_{k-1}) |$

G: Gini coefficient
Xk: cumulated proportion of the population variable, for k = 0,…,n, with X0 = 0, Xn = 1
Yk: cumulated proportion of the income variable, for k = 0,…,n, with Y0 = 0, Yn = 1

In the following program, I use yet another formula, which is even concise and straightforward:

(see Dixon et al. 1988, Damgaard and Weiner 2000)

Okey, the program itself:

#!/usr/bin/perl

my @origx=(20, 23, 18, 25, 28, 18);

my $gini=calc_gini(@origx); print "$gini\n";
exit;

sub calc_gini{

my @origx=@_;
my @x = sort { $a <=>$b } @origx;

my $ginisum=0; my$sum=0;
my $count=@x; for (my$i=1;$i<=$count;$i++) {$ginisum=$ginisum+(2*$i-$count-1)*$x[$i-1];$sum=$sum+$x[$i-1]; } my$gini=$ginisum/($count-1)/$sum; return$gini;

}

References:

Damgaard, C. and Weiner, J. "Describing Inequality in Plant Size or Fecundity." Ecology 81, 1139-1142, 2000.

Dixon, P. M.; Weiner, J.; Mitchell-Olds, T.; and Woodley, R. "Erratum to ‘Bootstrapping the Gini Coefficient of Inequality.’ " Ecology 69, 1307, 1988.

### 好累的周末呀

Sunday, March 19th, 2006 -- By Jade

Joe 比萱萱小3周，他们两个当时常在一起玩。Joe是个难缠得小男生。因为他吃牛奶，鸡蛋和华生都过敏，所以脾气比较古怪。也难怪，看见别得小同伴吃好吃得， 自己不能吃，要是不小心占了一点，Joe得脸上立刻起大红包。起红包，算是轻得，严重的，Joe就会呼吸困难。相反，妹妹Keiko确即不过敏，脾气也好 很多。日本人天生的比较矮，萱萱从小就超出Joe很多。打起架，抢起东西来，当时的楼里同龄的小孩，除了小女孩Stasha可以和她平手，无人能及，算是 楼里一霸。所以，Joe到后来看见萱萱来了，几乎要抱起玩具立刻逃跑。我认为Misuko是个社会活动家，她因为出生在美国，所以英语几乎可以算她的母 语，楼里的人她都认识，还发起组织了Baby net 和 baby sitting exchange。不过，虽然她很socialized，确常常拿她的儿子Joe毫无办法，看着Joe以头撞地，只好答应Joe的不合理要求。说起 Taka，可是绝世好日本男人。都说日本男人不干活，可是这个Taka确不一样。我曾经看见他背后用日式背兜背着小Keiko炒菜,同时还得照顾着难对付 的 Joe。他一阵子还坚持每天晚上开车带 Joe出去，因为Joe只有坐车才能睡着，等Joe睡着了，再抱回家。

### 关于’小豆’

Friday, March 17th, 2006 -- By ET

‘小豆’, 源于六亩林的故事,也就是winnie the pooh啦.

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