Monday, August 30, 2004

Reconstructing stars

When you do interferometry, it is not uncommon to have a set of incomplete fourier component data of the image of the star you are observing. This article seems to provide a good way to do a good reconstruction which is hopefully better than the current ones (paragrah 5.2.)

Waste is good. Nuclear waste is better.

This article reminded of the words spoken to me by a person who made it big (professionally that is) in the area of nuclear waste processing. He mentionned to me that initially, within the French public sector, you really needed to come from the best schools in order to get the top spots except when it came to dealing with nuclear waste. Nobody would touch the subject with a ten foot pole. Years later, nuclear waste reprocessing became such a hot button because it was the only bottleneck of the nuclear power policy that he himself became a pretty important person and would have a definitive say on how the country would eventually deal with the issue.

Desperately seeking primes II.

So this new algorithm can figure out if a certain number is a prime in O(log(n)^6) as opposed to O(log(n)^12). So that would mean O(log(10^(10^7))^6) = O(10^(6*10^7))= a constant multiplied by a number with 6 million digits of operations instead of a constant multiplied by a number with 12 million digits of operations in order to find a prime that is worth it. Yes, that is quite an improvement.

Tick Tock, Five more days till a 5.5 earthquake hits Southern California or a model crashes into oblivion.

In a previous entry, I paralleled the belief that people had in earthquake modeling and spam filtering. Time is running out on this earthquake model....

Saturday, August 28, 2004

Like in the movie Brazil, it looks like there is a way to design an algorithm that devises human intent

How can one determine intent algorithmitically : a profound human feature, when only juries in courts of laws can determine it ?
Irrespective to the fact that Secure Flight seems to have its days numbered because of its inability to figure out that a Member of Congress like Ted Kennedy is not a terrorist or that there are a bunch of David Nelsons, the real question is : whoever came up with this most impressive capability needs to licence/patent it to the private sector because not even Google can make a difference between different David Nelsons. Are we getting to the point where the uneducated masses of flight attendants (they are not educated in screening people) can have access to defective databases and have a say-so on one's ability to move inside this country and do business ? Have we gotten to the point described in the movie Brazil where a squashed bug changes the life of a person by entering the wrong name of Buttle instead of Tuttle in one of these databases? Only time will tell....

The road less traveled by an autonomous car

When you are shopping for a vehicle that would sustain the DARPA Grand Challenge. You are thinking: maybe a pick-up truck is not enough, I need to put additionnal hardware on top of it. And then you watch these two videos. The next step of this endeavor is probably to build a radio-controlled car and try to grab some "good" advice ? I say "good" because the wise word includes a link to a library written in C++ and Java. With this type of help, how can you be expecting to beat the averages and be the best ? I am not sure.

Damping expectations..

In this article, Bose founders seem to be inclined to devise a new suspension system that promises to be revolutionary. When you drive with a woman that is expecting, you know that whole body vibration is indeed a concern:

" The unknown threshold value for adverse effects on pregnancy suggests a limitation on an occupational exposure to the lowest reasonable extent. "

that has only recently been looked into as a subject of study:

" Recent studies have indicated that female workers who become pregnant and are exposed to WBV can possibly have added risk factors such as miscarriages and other gynecological disorders. "

Thursday, August 26, 2004

Plumbers in Space.

And you thought being an astronaut was all Buck Rogers. Better be the best plumber there is if you want to get in according to this internal NASA HQ release :

All electric current readings for the water pump with the newly installed rotor were 'as expected for a normal operating pump', both without and with water flowing through it. No leaks were found. This unprecedented level of on-orbit repair on an EMU, a pioneering feat that finally regained cooling after over a year (!), is an important milestone: Its 'lessons learned' greatly advance engineers' understanding of how these spacesuits operate after being in zero-G over extended periods, and that clearly impacts our preparation for future long duration space missions.

Saturday, August 21, 2004

Reduction of D2 dopamine receptors reduce cognitive functions

it stops the brain from associating reward to visual cues associated with rewards. Hence monkeys work earlier and longer on tasks since they do not know when they are going to get rewarded. Uh....

Should Miami be evacuated ? (Doit-on evacuer Miami ?)

What are the chances that the sharp turn of Hurricane Charley turns out to be due to Nonnormality as seen in Generalized Stability Theory ? In a few words, many different climatic models do tend to refer to the largest eigenvalue of the linearized version of these models to make an inference on what they can predict: i.e. if the eigenvalues are all negatives, then the system is subcritical and will wither away. The problem with this assumption is that eigenvalues are only telling you something about an asymptotic behavior not a short term one. The other problem is that if you deal with the linearized version of a nonlinear system of equations (like the Navier stokes equation that governs fluid flows such as the air in a hurricane) and if nonnormality is large (it seems to be an accepted fact when dealing with fluid flow) there is a great chance that you will never have time to "live" close to the initial conditions of the system since transient growth will make your assumption on the linearization totally invalid. This is also a sign that scientists predicting hurricane paths do not seem to have understood a specific strong coupling between two different physical phenomena. What is concerning is that the first paper was published in 1994 and the second one in 1998....

Thursday, August 19, 2004

Live Clean -> Die Young

This study is rather interesting in that it parallels some fo the assumptions that polio developed in the mid-50s in the U.S. because of the access of the general population to sanitation:

" The belief that the polio virus is spread by contact with the feces of an already infected person has been offered as an explanation for the increased incidence of polio in developed countries such as the United States during the 20th Century. According to this theory, before the advent of modern sewage treatment plants and other improvements in public sanitation, virtually all individuals were exposed to the polio virus early in their lives when they were at least partially protected by maternal antibodies. Thus, they developed mild, non-paralytic infections, probably during infancy, which provided them with lifelong immunity. However, with better sanitation, both these early infections as well as the likelihood of receiving antibody protection decreased, resulting in greater susceptibility to paralytic polio. Thus, in the words of Smith:

Put simply, paralytic polio was an inadvertent by-product of modern sanitary conditions. When people were no longer in contact with the open sewers and privies that had once exposed them to the polio virus in very early infancy when paralysis rarely occurs, the disease changed from an endemic condition so mild that no one knew of its existence to a seemingly new epidemic threat of mysterious origins and terrifyingly unknown scope (p. 23).
This central theory regarding the spread of polio is supported, at least to some extent, by experiences in third world countries. During World War II, for instance, U.S. and British troops stationed in undeveloped countries were much more likely to contract polio than native peoples, who apparently had already developed immunity (Paul, 1971). Even in the 1970's, when individuals from developed countries came into contact with those from a country without a modern sanitation system, the incidence of paralytic polio was about twenty times greater for those from the developed country (Nathanson and Martin, 1979).
The above explanation for the transmission of polio is generally accepted and seems quite logical. However, the incidence of the disease in the United States during the epidemic years was very irregular, not only from year to year, but from area to area, apparently showing no relation to improvements in sewage treatment. The actual reason for this variation remains another of the polio mysteries. However, it has been suggested that this variability was possibly due to increased virulence of certain virus strains or the presence of environmental conditions that enhanced the disease's transmission (Nathanson and Martin, 1979). "

Grand Challenge Citizenship Issue.

I was reading the latest rules for the Grand Challenge and found out that only US citizens can be team leaders. The problem I have with this is that it excludes U.S. permanent residents from being team leaders. Not only do they pay taxes and live here, it is also apparent if you know the issues with the INS that it is sometimes beyond their control that they are not citizens as early as the law allows them to be. The law says that once you are a permanent resident, it takes 5 years before you can ask for naturalization. Right now the situation is a little bit better for people who start the process today but three years ago it was a mess. Between the time you submitted your application for a green card and getting it, it would take between two to three years to get it (check the current I-485 waiting list here.) And then you wait the five years required by law and then you have to wait between 6 or seven months to have your application Ok'ed (look up N-400 waiting list.) This is a long time given the fact that most people have lived in the country for years before even being allowed to start this process. ITAR restrictions for instance recognize the fact that if you submitted an application to being a permanent resident, you could be considered a U.S. citizen for all itents and purposes because in effect, you have made the choice to live in this country and be a full part of the economy. The rules of the grand challenge specify that no classified information should be used during the contest. So if the challenge organizers feel that no secret/senstive technology is really being transferred why would they exclude 10% of the population that is legally here and has demonstrated against the odds of a particularly inefficient branch of the government, their choice of staying here. I don't get it....

Wednesday, August 18, 2004

Tis the season....

Beautiful as it may, the perseids can also hurt you.

Polyharmonic to you maybe

I don't want to be nitpicking, but to me polyharmonic really means that after the application of the Laplacian a certain number of times, the function is zero. In here it just means that after a certain number of iteration of the laplacian, one is left with a bunch of diracs at every nodes of the spline. That's not nearly enough of a zero to me, but who am I to say this.....not a mathematician apparently.


Why do I get the feeling that you do not need supercomputer blades to do this job ?

contourlets or curvelets ?

What I really want to know is ? are the contourlets better than curvelets ? I cannot stand the suspense....

Catch IT if you can

This method of catching payloads from space is not new. I recall they lost some of them, hopefully that won't be the case for this one....

Tuesday, August 10, 2004

Is Failure an option ?

I don't get it, every time I read about the two recent crashes of X prize contestants, I get a sense these failures spell the end of the projects, at least from the journalist's standpoint. But why should they care, it is not governement's money and most importantly, it is because these projects are cheap that they can continue and have failures.

Saturday, August 07, 2004

At long last a Fast Multipole Method just for you.

The first page of this article nails exactly why other people have not looked at using this technique to solve their own equations (in my case the linear boltzman transport equation.) Maybe I can dig into this again now there is a new approach....

Friday, August 06, 2004

Look miserable...

... not because the terrorists have won in making you looking stupid but rather because, after years of research, the state of the art in identifying faces has still not been really solved (even though there are some promising leads as undertaken by Dave Donoho and Carrie Grimes.)

Thursday, August 05, 2004

Pulsing Mud Communication System

No we are not talking about the deliberate obfuscation of communication of the MUD people in Dilbert's cartoons.

When you are three thousand feet in the ground, the temperature is 200 C, the pressure is 20000 psi and you need to tell people what it is like to be down there. Well this is exactly the problem the folks in oil drilling face everyday. If you consider that drilling cost about 200 to 300 K$ a day, you want to have a better solution than just going ten feet with some pole, pulling it back out, check the soil it witnessed and iterate until you get to 3000 meters down. The solution was devised by Schlumberger as Logging While Drilling (LWD): in short they put a probe next to the drill and expect the probe to send info back up. The probe has nuclear materials, NMR capabilities and so on and it is pretty expensive.

So how do you send information back up from deep down ? Wi-Fi or RF Comms won't work because of the depth of the rock. Resistivity or something equivalent like sound along the poles ? It turns out most of these poles are crunched by the pressure once they are down, so the ideal measurements of conductivity you knew don't work deep into the ground: It is a very bad inverse problem. Schlumberger came up with an innovative means, use the water they send down to help the drill convey messages back to the communication station. When it comes back up, that water is mud. So the probe sends pulses through the water/mud and convey information back up. The data rate is astonishing too: 15 bits/second.

Dual use star trackers

In the latest Rosetta image released, one can find that the star tracker was designed as a dual use instrument besides just star navigation. This is not the first time a star tracker is used for another purpose. The star scanner of Galileo was eventually used as a science intrument after the probe had been launched. It also found something that was astronomically relevant. This was a pretty amazing feat since operational instruments like a bus instruments like a star scanner / tracker have a dedicated mission and have very few additional embedded attributes that would make them interesting for other purposes.