Seismic Imaging

I've picked up a couple of books on seismic imaging.    One is called, Seismic Imaging and Inversion:  Application of Linear Inverse Theory, by Robert H. Stolt and Arthur B. Weglein.    The other is Digital Imaging and Deconvolution:  The ABCs of Seismic Exploration and Processing by Enders A. Robinson and Sven Treitel.    Since the government is now on day 9 of its shutdown and it's illegal for me to work, I have some time to read.

Let's start by looking at the ABC book.    It starts with a preface warning us that if we want to see how this all applies to exploration seismology, we would be better of looking at either Seismic Data Analysis by Yilmaz or Elements of 3D Seismology by Christopher L. Liner.

From there, we move onto chapter 1, which introduces/reminds us of the basics of waves and geometric optics (I never formally studied geometric optics and have to confess what I picked up on my own felt dreadfully dull…).    It's actually a pretty fun read.


I will discuss my readings more in a later post.  For now, here is a test of mathjax:

\frac{\partial^2}{\partial x^2} u(x,t)=\frac{1}{v^2}\frac{\partial^2}{\partial t^2} u(x,t)

Posted by william in books, physics, 0 comments

Star Trek: Into Darkness (warning, contains spoilers!)

I saw Star Trek:  Into Darkness in 3D Imax opening night.  The 3D was excellent.   The action was impressive.  However, somehow I left disappointed.   I think it was the action.

I grew up as a Star Trek fan.  I enjoyed the original series.  It took awhile for The Next Generation to grow on me.   At one point, I could recognize an episode from either series from just a few lines.   The spinoff series of DS9 took me longer to get into.   The character development was excellent and eventually it won me over.  Voyager, I felt borrowed too much from the older series, but 7 of 9 was a welcome addition to the show.   Enterprise, I have to say, never grew on me...

So, what was it about Star Trek that drew me in?  Part of it was the aliens.   But, Star Trek has always had an optimistic view of the future and has raised interesting social and philosophical questions.   I think this is part of what left me feeling disappointed about the last Star Trek movie.   Ultimately, Star Trek is not about the action, but is about the story.

We open to a scene on a planet in the Nibiru system.   The crew is trying to save the planet without violating the Prime Directive.   Spock is willing to die to avoid violating the Prime Directive, but Kirk breaks it to save his friend.   This is in keeping with Kirk's character in that for him, his crew come before all else.    Some of the setup to this is a bit hokey in that there's no obvious reason why ship needs to be under water and to be exposed to the natives, but let's go with it.

Later, Spock tattles on Kirk for breaking the directive and Kirk is demoted--luckily only to first officer--he's called to Starfleet headquarters for a meeting and a terrorist attack occurs and much of the Starfleet leadership is decimated.   Kirk is then pressed to go after the enemy on a secret seek and destroy mission involving 72 (interesting choice of number) prototype photon torpedoes.   To accomplish this, he will have to launch a covert attack in Klingon territory.   This cries out, "Bad Idea!", but Kirk is enraged at the loss of life, including his mentor Pike and anger clouds his judgement.  Also, the version of Spock in this universe is not able to act as a counterbalance and urge him towards reason--at least initially.    Though Spock does urge Kirk to consider that it is not the Starfleet way to kill a man without trial.   This whole issue is a nice commentary on todays world of drone strikes, targeted killings, terrorism, etc.   Once underway, Kirk comes to his senses and decides to apprehend the terrorist (Khan) rather than kill him from afar as ordered.  So, we see that though there is a glitch in Starfleet, it still has the overall character that we appreciated in it's original incarnation of an organization more dedicated to exploration than to war.

I'll fast forward.   Towards the end, we find that the director has inverted the role of Kirk and Spock in the original Wrath of Khan and has Kirk as the one who has rushed into the high radiation zone (though this doesn't make sense as part of Spock's reasoning in the original one was that with his physiology he could survive long enough to do what was necessary--along with his view that the needs of the many outweigh the needs of the few) to save the ship--in keeping with his character and the way that events unfold in this version of the timeline.   We then are treated to a mirror of the scene in the original Wrath of Khan where Kirk and Spock exchange their farewells--but this version lacks the poignancy of the original.  Because, in the original, these men had been friends not just for part of the academy, but throughout a 5 year mission and had faced many troubles together.   That's part of the problem with the film--without the 5 year mission, the bonds that we're used to should not be least not to the same level as before...

The other problem I have with the film is during the fight scene between Spock and Khan towards the end, Spock really loses control and has to be calmed by Uhura.  This is a Spock without the control over his emotions that the original had--and there is not a reason given as to why.   Meanwhile, Kirk is saved by Khan's blood, which also seems to be a stretch--why didn't someone "bottle" that stuff for later use if it could be used to cure the dead?

At least by the end, the crew begins their mission of exploration and this version of Starfleet seems to have regained it's path towards exploration over war.   So, there are some things that are to like about this movie.   I think its commentary on how a free society can react to terrorism is well done and is in keeping with questions raised in the original series about race, religion, etc.   However, I think the original Wrath of Khan held more dramatic tension and stronger characters.   This version of Khan fell flat.    Also, the full implications of the altered timeline were not realized.   Finally, this version of Spock seems unbalanced.   We'll see how the next one goes....
















Posted by william in movies, 0 comments

Inferno (a novel)

I recently finished reading the latest Dan Brown book, Inferno:  A Novel.   As always, it was a page turner.

In college, I was an engineering physics major.  I had a slew of AP credits, so the only real humanities course I took was during my freshman year--a junior level science fiction course taught by Rabkin (which was truly an excellent course!   We read a different book every week.  We could only write a one page paper, so it was great for teaching us to tighten up our writing!).   In high school, I had another excellent course called, "Humanities" which tried to immerse us in the zeitgeist of the times--we would march through western history, exploring writings, art history, philosophy, and music of different periods.   It's a compelling way of learning.   I was also fortunate enough to take Latin in high school and to read the Aeneid, the Cena Trimalchionis, etc. in Latin--but otherwise, most of what I've encountered of the humanities has been in my copious free time.   Somehow, I have not read Dante's Inferno and after reading Dan Brown's book, it's definitely on my to read list!

I will skip over a discussion of the iconography and plot of the book except to say that it revolves around a problem raised by Malthus.  Writing in the 1800s, Malthus' essential observation was that while the growth of resources up to then was linear, the growth in population was geometric.   Given this, there would have to come a point where the population could no longer be supported by available resources.   He believed that famines, plague, etc. had managed to avoid the inevitable catastrophe from occurring by dropping the population, but that it was just a matter of time.   A character in Dan Brown's novel believes that Malthus was right and takes steps to try to deal with the problem.

Now, the question I wish to ask, is whether Malthus was indeed correct.   By simple evidence of the fact that we are here today without having observed his predictions coming true shows that at least his time scales were wrong.   Some have argued that through science, we've managed to beat Malthus--namely through the Green Revolution.  But as this blog points out, the Green Revolution was made possible through the expanding use of fossil fuels--which are limited.   So, perhaps we've merely been able to push off the inevitable.    However, it would appear that as societies become more developed and educated, they tend to produce less children and the population is expected to stabilize around 2050.   Given current resource levels, we may have centuries to think about better solutions--so, I don't see the same urgency that led to the drastic solutions of Brown's villain...

As a final note, one of the suggestions in the book was that population collapse, such as that which happened after the Black Plague in Europe led to the Renaissance--but what of Justinian's plague?  What of the Spanish Flu?  I find it hard to believe that pandemics have generally been beneficial for humanity.  Personally, I think that overpopulation is not the most pressing concern that we have to worry about today.   Climate change and our energy future is a different story...






Posted by william in books, 0 comments

Getting started with D3

As we move more to the web for showing data, there is a need for good plotting libraries.   We started using flot and eventually migrated to JQPlot which I've been fairly happy with for general plotting.  Lately, I've been hearing about D3 for more custom plots and thought I'd take a bit of time to learn more about it this weekend.

I just had a quick read of Getting Started with D3 by Mike Dewar.   I saw an excellent talk by the author (who works at related to data analysis.   Sadly, I wasn't terribly happy with the book.   Part of it is that the book is just incredibly short!   The idea of taking MTA data to look at was good, but somehow I think more examples could have been shown, or perhaps some more involved visualizations/interactions.   After reading the book, I have a basic feeling for some of what D3 can do, but am not sure if I could have learned the same information from simply looking through the web...Some introduction to SVG would have been rather helpful.

I may play with it a bit later for a few custom visualizations and see whether it is worthwhile...From the book, and the examples that I've seen, it is useful when you're wanting to do non-standard plots, otherwise, I think I'll stick with jqplot.

Posted by william in books, javascript, plotting, 0 comments

What's Math Got to Do with It?

Lately, I've been reading about education in the U.S. and the rest of the world.   Later, I'll write a longer post, but for now, I'll start with a review of What's Math Got To Do with It? by Jo BoalerOverall, I found this to be a rather compelling read.


The Problem

The introduction starts out with a fun math class that the author has attended.    The author  enters and the students are solving a problem.  Imagine that you have a merry go round and a skate boarder attached.  At some point, she lets go--calculate how long it will take for her to hit a padded wall.    She later gives her answer in in the solutions.   It's a fun problem.   It's broad enough to pull in some geometry, trig., and algebra.  The class she discusses is very involved, with students arguing about different approaches to the problem.  They go the board and show their ideas.  You could imagine an experimental session being included...She notes that it is the students rather than the teacher who ultimately solve the problem (it takes them 10 minutes).

This example allows her to raise the debate between the more traditional approach to math education, where the teacher lectures, then the students silently work problems, and the more "modern" approach where students are more involved.   This is a debate I often had with my dad about the advantages of drilling/memorization compared to understanding...The school system I grew up in leaned more towards understanding and experimented with many different systems (ahh....Cemral).   I have to say that I went through a period where math just somehow didn't seem rather relevant--until Calculus, where I could see how it applied to physics...But, back to the book, the author's worry is that far too many students in the US aren't just apathetic about math, but actually hate and fear it.   Far too few of us continue to advanced levels and given the trajectory of jobs, this is a disaster in the making....She then goes on to give a number of rather depressing statistics about how few students are going into math, our relative ranking in the world, etc.     Beyond jobs, you just need math to make sense of how the world works today--be it looking at the results of a medical study, to understand basic economics, etc.   She also discusses the disconnect between the math that people are often taught in school and how they apply it in everyday life (for example, even when students have math to do in their part time jobs, few use school based methods for it...).   Sadly, the teacher whose class was observed was told that she was no longer teach in the way she was doing--with a problem solving based approach.   Instead, classes had to be given with teachers lecturing and students quietly solving problems individually.   Tragic...

Some of the reviewers in Amazon made a rather unfair criticism of this book, claiming that much of the discussion is anecdotal.   In reality, the author has conducted studies of thousands of American and British students through middle and high school.   She then draws on these observations to make generalizations.   She uses a few particular representative cases to highlight general trends--because most people relate well to stories.

In the first chapter, she sets up the problem.   Namely, there is a huge disconnect between the way that mathematics is taught in many schools (in the US) and how it is practiced by mathematicians (and anyone who uses math professionally).   In real life, mathematicians pull across a number of sub-disciplines to solve a problem (she gives the example of Fermat's last theorem).  The other thing that she notes is that there is a certain persistence that professionals use that is not taught.   Finally, she notes that in the real world, people collaborate!    This is definitely true in my field of physics.  I've been extraordinarily fortunate to have had very good collaborators.   While each individual needs to do their best, the modern world involves a great deal of collaboration.   I think that the main thing to note is that mathematics, engineering, physics, etc. are "living" arts.   We learn a number of basics, but when we are confronted by new challenges, we have to use whatever's in our arsenal to solve a problem.   Often, the problems we're solving are hard and require the use of different people with different areas of expertise.  We need to bounce ideas of of each other.    It's not just a lifeless set of rules to be memorized for a quiz and forgotten...While the basics are definitely important (like kata are important for martial arts)--if that's all you do, then you miss the art, get bored, and move on....

In chapter 2, she mentions more about the math wars.  Here, she introduces us to her first encounter with a strange group of traditionalists  (see who hate modern approaches to teaching math.   Again, while I doubt that anyone would question the need to practice--different students need different approaches.  When I was in grad. school, I was an NSF GK-12 fellow for awhile, where we would go into middle schools and try to help math/science teachers improve their classes.   I remember demoing one lesson in a 6th grade classroom about probability.   I'd notice that one student didn't understand something, so I'd present it another way, and if she still didn't understand, I'd try yet again (we also did activities to drive concepts across).

What she worries about is passive teaching approaches, where a teacher lectures and then students just work problems, without real understanding.   After years of this, students lose their ability to do creative problem solving.  Here is a simple problem that she gives:

A woman is on a diet and goes into a shop to buy some turkey slices.  She is given 3 slices which together weigh 1/3 of a pound, but her diet says that she is only allowed to eat 1/4 of a pound.  How much of the 3 slices she bought can she eat while staying true to her diet?

Unfortunately, many adults have problems with this.  You could set up an equation to solve it--but pictorial solutions are also a good approach.  The most important thing is to set up the problem...

She also brings  up the interesting idea of contexts.   Apparently, in the 70s and 80s, math educators in the US thought that they could make math more relevant by making it less abstract and more concrete and applying it to everyday situations--but they abstracted the everyday situations too much so that people familiar with the real situation got into trouble with the abstract situation.   Here, the better approach might be to start with the fully complex problem and show how we abstract it to something "tractable" to get an idea for what may be going on.   This is not easy to do.   To maintain enough "richness" of the original problem, but to make it something tractable to someone less experienced...I may discuss this in another post.   Of course, the author mentions that there are some problems that are without context, but still beautiful...



In Chapter 3, the author begins to move towards possible solutions and better approaches to teaching math.  One approach she looks at is one where the students try to communicate their solutions using multiple representations (graphs, words, tables, etc.).   It's an interesting approach and also encompasses group work.   In the author's research, they compared performance of students taught in this manner, with those taught in a more traditional manner and found  superior results from this approach--and a higher enjoyment of math.


Another approach is the project based approach.   Here, projects lasted about 3 weeks and focused on a given theme.   For example, students might be told that the volume of an object was 216 and then they would think about what kind of object it could be.   Concepts were taught on an as needed basis...The difficulties I see with this approach are many.   It requires the teachers to be careful to get a good coverage of different areas of mathematics and the end of the day.   It also requires a lot of effort to choose the right problems--in short, it requires a high calibre of teacher.    However, on national exams, the project based approach school outperformed a standard school with similar demographics.

The key here, I think is that if the projects are well chosen, it would be more engaging than a drill/kill approach, so retention is probably higher--but it would take more involvement on the part of the teacher...This is also the view of the author--though she does recommend some books in her Appendix.



Multiple guess--Ack!   Her first comment is that national assessments in Europe are rarely multiple guess.  There's only so much you can learn from multiple guess---you can try to choose common mistakes--but I think you'd learn more from free response--but that would be much more costly and harder to standardize....

The other issue the author finds with the standardized tests in the US is that they emphasize procedure under timed conditions rather than actual problem solving ability...Also, the feedback is limited--they are just given a score--not a listing of areas where they are strong and where they need to improve.


The author suggests an alternative that she calls, "Assessment for learning":

1)  Communicate what is being learned and where they are going

(For example, understand the difference between mean and median.._

2)  Let them know where they are (how they're doing)

3)  Let them know what they need to do to improve...

Generally, comments are more effective than grades in getting students to actually improve...(Which may suggest that leader boards and such comparing students in math games and such may be counterproductive...)




Ability based grouping is an interesting phenomena.   It's something that I used to argue a lot with my dad and I have to say that I'm coming more around to his way of thinking.   In the US, tracking starts from a fairly early age and by high school, you have remedial, average, college, accelerated, and gifted tracks in subjects such as math.   It's very hard to move up in tracks...The idea is that it would make it easier for a teacher to focus on kids if they are roughly at the same level.  It gives more time to focus on the "slow" kids and doesn't hold the fast kids back.   I think it can be nice for the fast track--but the harm for slow track can be great.    In point of practice--a number of countries that are much more successful in math education on average, such as Finland and Japan do not employ it.  I think you run into all sorts of problems, ranging from different development rates ("late bloomers") to the fact that people in the lower tracks may simply give up...



Here is a chapter that I won't go into too much--but one observation of the author is that a number of girls are discouraged in math due to a lack of explanations.   Her claim is that they especially suffer when just given instructions, without clear reasoning, whereas boys are more likely to soldier on.



One important point that the author looks at is the difference between successful and less successful students--flexibility.   Low performing students are rather good at counting, but as problems get more complex, they don't abstract.   As time goes on, this becomes more and more of a challenge for them.  She then highlights some individual cases where she led a class to try to help low-performing students over a summer learn to treat numbers more fleibility.


A good start

Problems, puzzles, and toys oh my!   The author observes that a number of people who use mathematics professionally, had a lot of out of school experience with math.   They were encouraged to ask questions...


So, overall, I thought it was a good book.   There are some specifics that I've glossed over, but the most important thing is the approach.   Instruction which engages students and leads them to communicate with each other is more effective.   There aren't quick fixes...












Posted by william in books, education, 0 comments