Keeping your direction, don't just follow fashion

This Friday, Kevin Shang gave us a talk about multi-echolen inventory problem. It is very classical problem but there aren't many people focusing on this area. And the barrier to this area is higher than most other areas related to inventory theory. So most people like to chase research 'fashion'. Somebody told me that a few years ago, sessions of SCM are full of people. But in this Informs meetings, RM seems more popular. A lot of people talk about dynamic pricing etc.

But Shang sticks to multi-echolen inventory problem after he passed his qualify exam. And he told me that he will continue to explore this area. It should be appreciate. Although our field just like a branch of applied math, it doesn't mean that everybody should just apply similar math technics to different applications. Once the math is too hard to go on in one area, then everybody shift their research interests. I don't mean that we shouldn't do so. In contrast, we need some people to do so to spread out our field. But what I mean is that we need some people to develop some unique math methods to solve those unsolved problems. Like developing in physics can push math forward. Why won't our IE people do the similar things? (Btw: I am not talking about those optimization people in IE fields)

Actually, I am a guy, who cannot focus on one thing for a long time. I like to find tons of applications, which can be easy in math. But I will find an area which can attract me for at least ten years. Of course, I will do other things on the same time.

What should I do in the next Informs meeting?

• Since I already get to know some friends from this conference, I hope I can meet each one individually and have deep conversation. Also because, I will have more time to do research from the fourth year, I hope to seek more opportunities to work on the different subjects with different people with their own expertise
• Prepare some deeper work to present. That's the only way to impress people, so that they are willing to work with you if possible.
• Get to know job market
• Create the chance to talk with those faculties
• Last but the most important, live at a hotel nearby the convention center. I run into trafic every day and get too less sleep every day during conference. And I haven't recovered yet.

internal force(nei gong) or external technic(zhao shu)?

I went to an Informs conference from Nov. 4 to Nov. 8. Everything goes well. Meeting and making friends is the most important thing for me since our department only has very few people sharing the same interests with me. I need to extend my network. Second thing is to present my work. It is ok since nobody left during my talk and I got two questions and handled well in my opinion.

But there is one fundamental question occuring several times during the conference. On one hand, we need to have good papers before we graduate. It means that I need to work hard on generating papers, which implies that I need to read a lot of literature. As Long told me that we need to accumulate several tricks which are used by different authors again and again in their papers but no one collect and publish those as a reference book. This is absolutely right. Even those great mathematicians has only a few tricks. On the other hand, I like to take as much courses as I can since I believe only when you have complete skill set, you can consider problems from different angles which gives you more insight. Also you can do something crossing the different fields.

In Chinese Wuxia novel, there are two kind of persons. One is working on internal force(nei gong) . It takes a long time to master. The other person is working on external technic(zhao shu). It is fast to learn but easy to hit the bottleneck. In the short run, the people working on zhao shu can easily beat the previous type of people since the stuff they learn is more practical. But in the long run, the previous people can outperform the people only having zhao shu since it has more power.

In this conference, when people start to talk about those 'famous' people's name, I feel a little bit embarrassing since I cannot recognize a lot of those 'big' names. I start to think whether I spend too much time in taking course other than reading related literature. For example, the next semester, I plan to take two courses and audit another two courses again. But I stick to finish those courses since I won't get any time to do so after I graduate. And only when you have enough nei gong, you can pick up those tricks quickly. I am not worried about my ability to come up ideas. Actually, during this Informs, I generate several new ideas. For now, I need to focus on developing those nei gong and try to work on only one or two ideas. After next semester, I would devote most of time into research but not now.

MSOM 2006 submission statistics

Till the latest data, there are 154 submission for the regular issues and 36 submission for the special issue.

For the regular issues, there only 4 papers(2.6%) get accepted. Among these 4, there are 2 papers get accepted without going through review process. 8 papers(5.19%) get minor revision and 35 papers(22.73%) get major revision.

For the special issue, 4 papers(11%) get major revision and 4 papers have got the decision. All other paper got rejected.

You can access data from http://msom.pubs.informs.org/msomdata.xls

The accpetion ratio is very low. MSOM currently publishs 4 issues a year. And each issue contain around 6 papers. So the acception ratio is around 24/(154+36)=12%. That means around 2/3 major revision paper will get rejected finally.

Lehigh ranked 18th undergraduate B-school

It is a little bit surprising to see Lehigh can get 18th rank in that category. ANyway, it is still a good news.

Beamer's columns

\frame
{
\frametitle{Interview}

\begin{columns}
\begin{column}{0.5\textwidth}
\begin{itemize}
\item current symptoms
\item past medical history
\item family history
\item social history
\item review of systems
\end{itemize}
\end{column}

\begin{column}{0.5\textwidth}
\begin{itemize}
\item detect hypertension
\item recognize emergency
\item recognize reversible causes
\item find chronic target organ damage
\item discover co-morbid conditions
\item plan therapy
\end{itemize}
\end{column}
\end{columns}
}

You can have as many columns, of whatever widths, as you like. Note that
within a column, \textwidth will correspond to the column width, not the
width of the beamer slide, so it works pretty much like minipage.
Material within columns is vertically centred, and you can have part of
the slide in normal (single column) format, and other parts in more than
one column.

Insert List into Tabular in Latex

Here is the code. But I still cannot figure out how to do under Beamer. The ultimate goal is to insert the Figure into the left top corner and put the list on the right.

\documentclass[12pt]{article}
\makeatletter % Yes, it's horrible
\def\spacehack{%
\@minipagetrue% % Disables spacing above
\expandafter\everypar\expandafter{% % Add stuff to \everypar
\the\everypar% % Do what was there before
\@minipagefalse% % Clear the mystic flag
\everypar={}% % And reset \everypar
}%
\let\@oldbs=\\% % Remember old \\ command
\def\\{\nointerlineskip\@oldbs}% % Turn off final odd spacing
}
\makeatother

%
\begin{document}
%
\begin{tabular}{p{40mm}p{40mm}p{40mm}}\hline
& Advantages & Disadvantages \\ \hline
Method 1 & \spacehack\begin{enumerate}
\setlength{\itemsep}{-\parsep}
\item item one
\item item two
\item item three
\end{enumerate} & \spacehack\begin{enumerate}
\item item one
\item item two
\end{enumerate} \\[-12pt] \hline
Method 2 & \begin{enumerate}
\item item one
\end{enumerate} & \begin{enumerate}
\item item one
\item item two
\end{enumerate} \\ \hline
Method 3 & \begin{enumerate}
\item item one
\end{enumerate} & \begin{enumerate}
\item item one
\end{enumerate} \\ \hline
\end{tabular}

\end{document}

How to be a good lecturer?

You need

• Have interesting problem (not to be too hard and too specific, especially when your audience background is mixed
• Always talking something that is easy to understand.
• More figures than words and formula
• I will add more here

How to be a good listener?

From those experience, I see there are several keys to be a good listener.

• Try to understand the main point
• Try to answers all the questions other people ask
• Try to think all possible ways to attack their theory
• A good lecturer is neccessary

How I remember those speakers' presentation(2004, Fall)?

Yesterday I read through the advice to the young scientist. It gives some advice about how to do a good talk. The first advice is 'Every lecture should make only one main point. ' And the fouth advice is 'Give them something to take home.'. What can make people remember you. Here is the answer.

It is not easy to follow this advice. It is easier to state what features of a
lecture the audience will always remember, and the answer is not pretty.
I
often meet, in airports, in the street, and occasionally in embarrassing
situations, MIT alumni who have taken one or more courses from me. Most of the
time they admit that they have forgotten the subject of the course and all the
mathematics I thought I had taught them. However, they will gladly recall some
joke, some anecdote, some quirk, some side remark, or some mistake I made.

So I want to recall all the seminar in our department I attend to see what I remember from those talks. Then I may know how to improve my presentation. And how to be a good audience. Here I need to clarify. The talks I don't remember now may be due to that I don't have enough knowledge at that time. I begin from 2004, Fall which is my first semester here.

2004 Fall, I attended all the seminars. The following is the talks that I still have an impression.

08/27/04 David Drake Lehigh Phd student: This is first seminar I attended. The only thing I still can remember is that he thought HongKang is nice place.

9/17/04 Suvrajeet Sen. Program director at NSF. This was the time that every professor was going to take notes. I remember that Dr. Ralphs and Linderoth asked some questions about software patent.

11/5/04 Aurelie Thiele. Lehigh. I know newsboby model can also extend to revenue management. But the terminology is different. Basically, for the simple concave problem, the optimal solution is achieved at marginal cost equal to marginal revenue. In the revenue management, if we have high fare class and low fare class. The number of seats reserved to high fare class is achieved at expected revenue brought by high fair class is equal to expected revenue brought by low fare class.

12/3/04 Krishnan Anand, Upenn, There was an interesting situation that sometimes information may cause increase of inventory. I also remember there is an question related to Wal-mart. Later on, I find a good explanation and email it to Prof. Anand.

An example of converge in probability but not almost sure converge

This is one homework question in stochastic process class. I cannot come up even one example by myself. First I use goole, nothing valuable is found. Then I http://books.google.com/. I get a book named 'Counterexamples in Probability and Statistics'. The example is X_n=H_n, where H_n is Bernoulli variable with probability 1/n to be 1. X_n converge to 1 in probability. But Prob(H_n = 1 infinity often)=1 by Borel Cantelli Lemma.

2 hours to clearn up the inbox

I store all the emails in the box and only delete some when I get the warning about storage. Last time I did clearning is last semester. Today I spent 2 hours to move every email to the proper local folders. It is a good chance to see what I have done since the end of last semester. Although the outcome of research isn't that breakthrough, I am still satisfied with how I deal with those multi-tasks. Now I have fewer things to do. I can put more emphasis on each thing I am doing.

Advice for the Young Scientist

Another related article mentioned is Ten Lessons I Wish I Had Been Taught

My presentation@IP seminar: "rondom thoughts about optimization"

Yesterday I did my first outside class presentation Since my research is not mainly about optimization, I have to make up some stuff to fit the audience's interest. Also I hope that my talk can create some coordination between students in our department. So I just provide several of my ideas which I think that might be attractive to other people.

The result of presentation is OK, at least people don't feel bored during that 50 min. But I am sure that I don't achieve my target fully, since no one shows strong interests. Larry told me that my confidence overcomes my spoken English. Prof. Huang shows a different approach to solve one of my problems about LP and regression after presentation, where there is no need to change matrix A but only constants on RHS. Also I find another way too. We can just change one column instead of replacing the rows. Prof. Linderoth also provides me how do sampling in multi-stage stochastic programming. Prof. Ralphs reminds me how to get dual solution easily. Ash shows interest on my network formulation and I explain to him about bootstrap idea further. Zumbul told me that she has her own problem and want to coordinate with me. Finally my wife told me that I put too much contact with those professors and lose contact to the students.

Finally, I should say I need focus. After that I hope get any coordination with other students.

I have three SCM books now

After struggling for a while, I final decided to buy two more SCM books. They are

• The logic of logistics
• Foundations of stochastics inventory theory

Plus I already have

• Foundations of Inventory Management

Also I copy

• Inventory Control

What else do I need to collect?

The best deal for the Economist ever

Today when I got books from Amazon. I found such good coupon. There is only $100 for 51 issues of Economist plus $25 Amazon coupon. I wish that I could have to read.

Prediction of Nobel Prize in Economics 2006

I guess it would belong to Bhagwati, Dixit and Krugman since their topic is more interesting to me.

measurable or nonmeasurable

Now I am doing Real analysis homework, it is hard to imagine those strange sets. The course till now is all about trying to show that close properties about measurable set and functions. It is hard to come up your own counter example and deal with those 'strange' stuffs like Cantor, Borel, nonmeasure sets.

Luckly by keeping doing the homework even though the score is as normal as my other courses, I am still not lost in the class. It should be considered as the hardest course among all ones I take and audit. Maybe it is time to go office hour next time.

Arby's coupon

Yesterday night, I came to Arby's to have my dinner to save my time. I use the coupon Arby's sends out to me every month. I just raised my hypothesis before I order:
People eat insides are more price intensive so that more people use coupon than those who drive through.
Supposing my hypothesis is true, if Arby's send out the coupon to everyone no matter whether they prefers to eat inside or drive through, then it may lose potential revenue since it increases the chance of using coupon among the driving through persons. After I observe during my dinner, four transaction occurs all including coupon. That increases my confidence on my hypothesis.

A naive way is to replace current strategy with only putting coupon inside the store.

Again, we can build a model to help Arby's to improve their revenue

oonumerics.org

It provide information about different package in the following catogories

• Linear Algebra
• Arrays and Images
• Neural Networks, genetic algorithms, machine learning, data mining
• High-Energy Physics and Quantum Chemistry
• Multiprecision, arbitrary precision data types
• Differential Equations
• Automatic differentiation and interval arithmetic
• Visualization
• Graph Theory/Combinatorics
• Language interoperability/scripting
• Transforms
• Optimization
• Miscellaneous
• Tools

But there are several packages in each catogory. If there is someone providing comparison, it will be great.