An inconvenient truth

Tonight I watch 'An inconvenient truth' again. It presents such a shaking fact - global warming. I suggest that everybody should watch this movie.

I should remind to turn down light every minutes.
Buy hybrid car for next new car.
Let everybody know TSP problem.

But when people tell you that our earth is going to destroy. What would you do? Take action to save it by controlling your desire or Do what ever you want to do before it is too late?

Trailer
http://video.google.com/videoplay?docid=2078944470709189270
http://www.climatecrisis.net/trailer/

Official website
http://www.climatecrisis.net/

Download
http://www.climatecrisis.net/downloads/

10 things should do
http://www.climatecrisis.net/pdf/10things.pdf

Chat Center

There has been enomous study on the call center. MS has special issue on the call center back to 2004. Last week, I found there is potential another variation of call center. I call it chat center. There is a problem after I reinstall my computer. I find email response is too slow. Therefore I choose to chat to solve my problem. I find it is effective way to solve complex problem rather than email and phone. After my case got solved, I begin to ask that representives some questions and get some answer:

Question: How many customer do you serve every day. just curious
Answer: It depends, but as we try to sort and help out each of our
customers, it is normally 12 to 15 customers on an average.
Question: Is it possible that you can serve two or more people at the same
time
Answer: Yes, at times when there are chats waiting we have to attend two
customers at the same time.
Question: As I remember there is checkbox at the beginning to let me import
what kind of questions do I have. Does that mean you can solve all the cases?
Answer: We have all the tools that are needed to resolve all the hardware
issue, every customers issue is different and sometimes almost same.
Question: Just another question, how do you balance between two or more
people at the same time?
Answer: We attend at the maximum 2 customers and that too only if the
volume of chats is too high.
Question: What if both people doing something else so that no one respond
you in time?
Answer: This gives me more time to search and try to find out more
solutions.

Usually each server in the call center can only serve one people. But in the chat center, each server can serve more than one people. But now we cannot assume the service time is exponential. Otherwise your previous service time is useless. It is more like CPU case. But CPU job is deterministic. The order of serve in the CPU may not affect system performance that much. But human being is a totally different story. Which model is good, how to get system performance, how should representives balance service to more than 2 people?

Another application of chat center is MSN messenger. Some companies use msn to serve their customer. This might bring another whole bunch of interesting issues. How to balace of messenger service and current work? When to use messenger, when to use phone?....

We should always keep our eyes open to our daily life.

Where is Killer Application of OM

Yesterday, I kept talking with different people. One is a graduated phd student from our department. He was used to work on inventory management in one Fortune 500 company. But the salary cannot compete with phd student from other field such as EE. We both feel that OM such as inventory theory (I doesn't mean those technology such as decreasing leadtime, since it has nothing to do with model) doesn't bring much improvement for the companies. For example, in the EOQ model, the model is quite insensitive to order quantity. And a lot of computation studies exclude cost such as purchase cost in order to emphasize the benefit of the model. Not to mention the restriction of the model. That might be low recognition of our field. I bet the number of people knowing IE would be less than 1/n knowing EE, ME... Why? Because those fields bring the more value to the society. People's live get changed by those fields.

Just like the slow progress of 3G, the lack of killer application obstructs development of 3G technology. The lack of killer application of OM/OR prevents smart people entering into this area and limits the amount of funding. We need more applications using OR/OM techniques to create great value to companies or even bring new companies.

Hope one day papers in our field are not just to improve the existence practice but also bring new model which companies would look into. Like CPLEX would send people to academic conferences. If more and more companies send their employees to OM ones. Also we have more master degree program other than MBA to train manager to have more quantitive competence. Then I would think our field gets recognized.

My research life approachs complete one more step

From winter break, I am doing on something which I feel very good. And I spend a lot of time to do literature survey to make sure no one did similiar thing before. Then I began to do proof and write a journal-like notes with 20+ pages. But yesterday, I read a paper published in top journal which is a special case as my idea. Although I did something else and proof is different, I still feel very very frustrated. I received Larry's comfort email. After one night sleep, I feel a little bit. And I also chat with my college friend who is top researcher in my mind. It makes feel better also. Our chat history is attached in the comments. Chinese is mine and English is my friend.

The power of the blog

As blog gets more and more popular, it becomes a source for the companies to advacate their products and improve their service. I remember there is a market research company which analyzes the blog posts and sell their analysis reports to its clients. Not it seems the companies take more preactive role here.

As I post the comments about dell product days ago. I receive the following email.

I am a customer advocate here at Dell headquarters in Texas. I found
your blogspot post about the problem you had with the motherboard on your Dell
Inspiron 600m (http://bsaint.blogspot.com/2007/03/balance-of-product-quality-and-warranty.html).
I wanted to check with you to see whether the replacement fixed the
problem. If you had any questions for me I would be more than happy to
answer them.

Today, the new motherboard is installed. It seems the problem is solved.

Responsible Authorship and Peer Review

James R. Wilson provides nice introduction about authorship and peer review.
When you write a paper, we should remember

If you’re doing an experiment, you should report everything that youthink might
make it invalid—not only what you think is right aboutit: other causes that
could possibly explain your results; and thingsyou thought of that you’ve
eliminated by some other experiment, andhow they worked—to make sure the other
fellow can tell they havebeen eliminated.

He also gives several things to check as a reviewer. Although I never review any paper, it is good to keep those questions in your mind when you write a paper.

1. Are the problems discussed in the paper of substantial interest? Wouldsolutions
   of these problems materially advance knowledge of theory,methods, or
   applications?
2. Does the author either solve these problems or else make a contributiontoward a solution that improves substantially upon previous work?
3. Are the methods of solution new? Can the proposed solution methods beused to solve other problems of interest?
4. Does the exposition of the paper help to clarify our understanding of thisarea of research or application? Does the paper hold our interest andmake us want to give the paper the careful reading that we give toimportant papers in our area of specialization?
5. Are the topic and nature of this paper appropriate for this journal? Arethe abstract and introduction accessible to a general reader of thisjournal? Is the rest of the paper accessible to a readily identified group ofreaders of this journal?
6. Are the clarity and readability of the manuscript acceptable? Is thewriting grammatically correct?
7. Does the manuscript contain an adequate set of references? Is adequatecredit given to prior work in the field upon which the present paper isbuilt?
8. Is the material appropriately organized into an effective mix of text,figures and tables? Are data given in tables better presented in figures orin the text?
9. Is the work technically correct? Are the main conclusions justified by theexperimental data and by logically valid arguments? Are the theoremsstated and proved correctly given the assumptions? In practicalapplications of the theoretical results, do the authors check the validity ofthe underlying assumptions?
10. Are there gaps in the discussion of the experimental methods or results?If there are such gaps, can the closing of these gaps be considered (i)essential, (ii) desirable, or (iii) interesting? Are the experimental methodsdescribed in sufficient detail so that other investigators can reproduce theexperiments?
11. Have the authors explicitly addressed the limitations of their study—thatis, have they adhered to Feynman’s ideal of “utter honesty” and “leaningover backwards” in reporting their results?

One more step closer to finish all the courses

I just submit my mid term take home exam for IP class. Now there are 2 final, 2 projects remaining before I finish all my desired courses to take. There are still some courses attracts to me. But I will only audit them and focus on doing research and make some progress.

A useful integral identity

$(\int_{t}^{T}\sigma(t,u)du)^2-\int_{t}^{T}\sigma (t,u)\Sigma (t,u)du\equiv 0$ where $\Sigma (t,T)=\int_{t}^{T}\sigma(t,u)du$
This is the identity I found when I derive bond price under Q measure in the homework.

Lattice Search

Suppose f(x,y) is a convex function. Now we want to find optimal integer x* and y* to minimize f(x,y) over integer set.
In continuou case, if we know x*(y), then we can just minimize f(x*(y),y) by taking derivative.
In discrete case, if we know x*(y), then can we say that -f(x*(y),y) is unimodular?

The balance of product quality and warranty

Today Dell agreed to change the motherboard for my laptop after I complained that my laptop sometime automatically turn off when I use battary only. I also change the touch pad last year due its insensitivity.

Almost 2 years ago, I buy this 600m with half price. In order to do that, I need to find a configuration above 1500. Maybe unlike other people, I only choose to increase meory then I select 4 year at home warranty, since I cannot trust dell's quality 100%. And I don't like play game and don't do computation in my laptop. I think this laptop can still be used until my graduation if there is no big problem. Now this decision is rewarded.

But why dell cannot improve its production quality when he knows this product has 4 year warranty. I remember it cost about 250$ to increase from 1 year to 4 year warranty. But the change of motherboard is not that cheap. Consider anther 2 years to go, dell may lost money in my laptop heavily.

Companies like dell which has the information of customer order before its production, should be able to determine the suitable quality for its product based on warranty duration.

Inside the box

'In my career, I've found that "thinking outside the box" works better if I know what's "inside the box". In music (as in life), we need to understand our pertinent history, and moving on is so much easier once we know where we've been' ---Dave Grusin (Award winning composer and jazz musician)

This is what I got from Starbucks cup yesterday.

XP to inventory problem

Here XP is the product of microsoft. X can be substituted by I, L, NL, D, S....
Yesterday, I try to read the paper about multilocation and multiperiod model by Karmarkar (1981). Originally when I saw programming form. I think I can handle it without too much difficulty considering quite amount of time I devote to those XP classes. But it turns out that I am still lost finally. That's why everyone need to focus.

But I think using XP especially constructing dual problem will help us increasing the understanding of the inventory problem more. In his paper, he shows that base stock is optimal policy under certain condition for example transshipment. And it follows monoticity properities.

Although I think there is a potential mismatch of his SNLP form and the transshipment application, I really like his method. At least it can be alternative method to show that base stock is optimal under single location without using DP and those derivative stuff. I think that we need to see more alternative methods to prove the same important stuff. Wish one day I can see a paper with name 'simple/alternative proof of xxx in inventory theory'.

If someday, there are erratum for those major journals. Although there is notes but that is not enough. Even the smatest and most rigorous people will make errors all the time. Also it would be very very nice to someone to discuss with you about the same paper that interest both. The understanding would be deeper. You will truely understand something when you teach/discuss with somebody. Also the new idea is easier to come out.

Why lost sales is still unsolved problem

These days, I read some papers about transshipment. There are two papers mentions why lost sales is hard to handle in general. This recall Zipkin's presentation about greatest unsolved problem in inventory theory. The reason is quite simple. If c(x) is convex, c(a(y)) is still a convex function when a(y) is affine function. But c([a(y)]^+) is not convex function in general. But it is still unimodal. After a little bit more thinking, another reason the authors not mention is that the sum of two unimodal may not be unimodal. That means unimodal doesn't perserve under expectation. So base stock policy may not be optimal policy. Hope I can a paper about lost sales to confirm this is the major reason to impede the discover of optimal policy form for lost sales.

OM in Health care

As my wife works at consulting firm for a pharmaceutical companies, I begin to know a little bit about the health care system in US now. It is quite surprising to me when I heard that american people spend every 1 of 5$ of their income in health care from the radio, although I know this industry is huge. Then the next question is natural based on my background. What our OM/OR people can do for health care industry. Obviously we cannot develop the new medicine to cure the cancer. But there is some ways that we can improve the efficiency, which is all what we can do.

The first example comes into my mind is that an example about the quantity of cancer treatment in an LP book. The second example is how to minimize the total walking distance in the hosptial. But those are all about optimization model. We definitely can do more. The impact might be even more important than other industries such as airline which is consider the hot research area but suffer the hard time now.

Experience in Starbucks

I have been in Starbucks frequently especially this week as a spring break. My working efficiency improves a lot since you can do nothing without internet access except the papers, books and winedit. I am quite satisfied with the environment there. You can stay all day long even if you just refill water after buying 1.85$ green tee. And when you are thinking, you can walk around. The more you go to the shop, the more familiar face you will see. Although there is no conversation, you still feel warm.

But today, I really feel tired at 3pm after finishing IP homework. However, there is no place for me to have a nap. I spend almost 2 hours to read all articles in today's NY time. From business to sports, from politics to alternative energy. This might be the first time that I read the newspaper so intensive after I leave China. I still remember the time that I fall asleep with whole bunch of business newspapers and magzines. I hope one day my english reading speed can be half as my chinese reading speed. Then I can be informed again.